SECTION 6C2-1 - GENERAL INFORMATION –
V6 SUPERCHARGED ENGINE
IMPORTANT
Before perfo rming any Service Operat ion or oth er procedure described in this Section , refer to Section 00
CAUTIONS AND NOTES for correct workshop practices with regard to safety and/or property damage.
CONTENTS
1 GENERAL DESCRIPTION
1.1 POWERTRAIN CONTROL MODULE (PCM)
PCM SECURITY LINK
PROM
PCM MEMORY FUNCTIONS
1.2 ENGINE INFORMATION SENSORS
AND SIGNALS
CAMSHAFT POSITION SENSOR
ENGINE COOLANT TEMPERATURE (ECT)
SENSOR
EXHAUST GAS OXYGEN SENSOR
INTAKE AIR TEMPERATURE (IAT) SENSOR
MASS AIR FLOW (MAF) SENSOR
THROTTLE POSITION (TP) SENSOR
VEHICLE SPEED SENSOR (VSS)
A/C REQUEST SIGNAL
BATTERY VOLTAGE
CRANKSHAFT REFERENCE SIGNAL
ENGINE COOLING FAN SIGNAL
TRANSMISSION POWER/ECONOMY SWITCH
THEFT DETERRENT INPUT SIGNAL
OIL PRESSURE SWITCH
1.3 AUTOMATIC TRANSMISSION INFORMATION
SENSORS AND SIGNALS
1-2 (A) AND 2-3 (B) SHIFT SOLENOID VALVES
3-2 CONTROL SOLENOID VALVE
TRANSMISSION PRESSURE CONTROL
SOLENOID
TORQUE CONVERTER CLUTCH SOLENOID
VALVE
TORQUE CONVERTER CLUTCH PWM
SOLENOID VALVE
TRANSMISSION FLUID PRESSURE (TFP)
MANUAL VALVE POSITION SWITCH
VEHICLE SPEED SENSOR
AUTOMATIC TRANSMISSION FLUID
TEMPERATURE SENSOR
TRANSMISSION PASS-THROUGH CONNECTOR
1.4 FUEL CONTROL SYSTEM
PURPOSE
FUNCTION
MASS AIR FLOW SYSTEM
MODES OF OPERATION
CAMSHAFT POSITION SENSOR
SHORT TERM FUEL TRIM
LONG TERM FUEL TRIM
LONG TERM FUEL TRIM CELLS
BASIC FUEL SYSTEM OPERATION
SYSTEM COMPONENTS
1.5 IDLE AIR CONTROL (IAC) VALVE
1.6 DIRECT IGNITION SYSTEM (DIS)
PURPOSE
OPERATION
SYSTEM COMPONENTS
DIRECT IGNITION SYSTEM (DIS)
NOTEWORTHY INFORMATION
1.7 ELECTRONIC SPARK TIMING (EST)
HOW DTC 41 AND 42 ARE DETERMINED
RESULTS OF INCORRECT OPERATION
1.8 ELECTRONIC SPARK CONTROL (ESC) SYSTEM
PURPOSE
OPERATION
1.9 EVAPORATIVE EMISSION CONTROL
RESULTS OF INCORRECT OPERATION
1.10 ELECTRIC COOLING FAN
ENGINE COOLING FAN LOW SPEED
ENGINE COOLING FAN HIGH SPEED
1.11 A/C CLUTCH CONTROL
1.12 A/C REFRIGERANT PRESSURE SENSOR
1.13 SUPERCHARGER SYSTEM
DESCRIPTION
SUPERCHARGER OPERATION
BOOST CONTROL
OPERATION
RESULTS OF INCORRECT OPERATION
DIAGNOSIS
1.14 ANTILOCK BRAKING SYSTEM / TRACTION
CONTROL SYSTEM
PURPOSE
1.15 ABBREVIATIONS AND GLOSSARY OF TERMS
Techline
1. GENERAL DESCRI PTI O N
This engine, with an autom atic tr ans miss ion, uses a Powertrain Contr ol Module ( PCM) to c ontrol ex haus t emiss ions
while maintaining excellent driveability and fuel economy. The PCM maintains a desired air/fuel ratio of precisely
14.7 to 1 by m onitoring electrical signals f rom dual oxygen sensors m ounted in the exhaust stream and optimising
the amount of fuel flow from the injectors. This method of "feed back" fuel control is called CLOSED LOOP.
In addition to fuel control, the PCM also controls ignition dwell and timing, idle speed, electric engine cooling fan,
electric fuel pum p, ins tr ument "Chec k Powertr ain" Malf unc tion Indic ator ( MIL) and, on vehicles so equipped, the A/C
compressor clutch. The PCM controls the automatic transmission functions and also interfaces through the serial
data line with other vehicle control or information modules, such as the Instrument, Body Control Module (BCM),
ABS/TCS m odule, OCC m odule and SIR m odule. Figure 6C2-1-1 c ontains a list of the various operating conditions
sensed by the PCM on the left, and the various systems controlled, on the right. Details of basic operation,
diagnosis, and service are covered in this Section.
The PCM has a built-in diagnostic system that recognises and identifies possible operational problems and alerts
the driver by activating the "Check Powertr ain" Malfunc tion Indicator Lam p ( MIL) on the instr um ent panel. If the MIL
is activated while driving, it does not m ean that the engine s hould be stopped im m ediately, but the cause of the MIL
being activated should be chec k ed as soon as is reas onably possible. The PCM has built- in back up sys tem s that in
all but the most severe failures will allow the vehicle to operate in a near normal manner until repairs can be made.
Below the instrum ent panel and the steer ing colum n is a Data Link Connector (DLC) which is used by the ass em bly
plant for a c omputer "c hec k-out" of the s ystem. This c onnec tor is us ed in s ervic e together with the Tec h 2 scan tool,
to help diagnose the system. Refer to Section 6C2-2, DIAGNOSIS for further details.
The locations of the engine management components of the system are shown in the following Figure 6C2-1-2
through 6C2-1-6.
For the automatic tr ansmis sion management system c omponents and their locations , r ef er to F igure 6C2- 1-7 in this
Section.
Figure 6C2-1-1 V6 Supercharged Engine Powertrain Control Module Systems
Figure 6C2-1-2 – V6 Supercharged Engine Compartment Component Locations
Legend
1. Fuel Tank
2. Fuel Pump (Inside Fuel Tank)
3. ECC In-Car Air Temperature Sensor
4. Fuel Pressure Regulator
5. Heated Exhaust Gas Oxygen (HO2S) Sensor (Two)
6. Bypass Valve Actuator
7. Engine Coolant Temperature (ECT) Sensor
8. Boost Control Solenoid
9. Throttle Position (TP) Sensor
10. Idle Air Control (IAC) Valve
11. Engine Harness (PCM) Ground (Two Terminals)
12. Fuel Injectors
13. Intake Air Temperature (IAT) Sensor
14. DIS Module
15. Mass Air Flow (MAF) Sensor
16. Tachometer Lead
17. Powertrain Control Module (PCM) (Inside Vehicle)
18. Air Cleaner
19. Ignition Coils
20. A/C Refrigerant Pressure Sensor
21. A/C Accumulator
22. Engine Cooling Fans (Two)
23. Crankshaft Position (CKP) Sensor
24. Oil Pressure Switch
25. Camshaft Position (CMP) Sensors
26. Detonation Knock Sensors (KS) (Two)
27. Engine Harness (PCM) Ground (Two Terminals)
28. Battery
29. Engine Compartment Fusible Links
30. Engine Compartment Relays
31. Engine Compartment Fuses
32. Anti-Lock Braking System (ABS)
33. Brake Hydraulic Failure Switch
34. EVAP Canister Purge Solenoid
35. Diagnostic Link Connector (DLC)
36. Body Control Module (BCM)
37. Check Powertrain Malfunction Indicator Lamp (MIL)
38. Fuel Pump Control Module (Rear Compartment)
39. Vehicle Speed Sensor (VSS)
Figure 6C2-1-3 – Engine Compartment Fuse/Relay/Fusible Link Locations
Legend
Fuses
1. Fuel Pump Fuse – F28
2. Engine Control / BCM – F29
3. RH Headlamps – F30
4. LH Headlamps – F31
5. Automatic Transmission – F32
6. Engine Sensors – F33
7. Injectors / Ignition – F34
8. Injectors / Ignition – F35
Relays
9. Start – X1
10. Blower Fan – X2
11. Headlamp (High Beam) – X3
12. Engine Control (EFI) – X4
13. Engine Cooling Fan (High Speed) – X5
14. Horn – X8
15. A/C Compressor – X11
16. Fog Lamp – X10
17. Fuel Pump – X16
18. Headlamp (Low Beam) – X14
19. Engine Cooling Fan (Low Speed) – X7
Fusible Links
20. Engine Cooling Fan LT (F101 (30A)
21. Blower Fan – F106 (60A)
22. Main – F105 (60A)
23. Engine – F104 (60A)
24. A.B.S. – F103 (60A)
25. Lighting – F102 (60A)
26. Engine Cooling Fan RT (F107 (30A)
Figure 6C2-1-4 – V6 Supercharged Engine Component Locations
Legend
1. Throttle Position (TP) Sensor
2. Idle Air Control Valve (IAC)
3. Boost Control Solenoid Valve
4. Engine Coolant Temperature (ECT) Sensor
5. Injectors
6. Direct Ignition System Module
7. L.H. Knock Sensor (KS)
8. Crankshaft Position (CKP) Sensor
9. Ignition Coils (3 places)
10. Bypass Valve Actuator
910
5
8
7
4197
6
12
3
4
Figure 6C2-1-5 – V6 Supercharged Engine Component Locations
Legend
1. Injectors
2. Canister Purge Solenoid
3. R.H. Heated Oxygen (HO2S) Sensor
4. Transmission Pass-Through Connector
5. Vehicle Speed Sensor (VSS) (Automatic Trans)
6. PCM Connectors
7. Engine Harness Ground
6
7
4199
1
2
3
4
5
Figure 6C2-1-6 – V6 Supercharged Engine Component Locations
Legend
1. Ignition Coils (3 places)
2. Fuel Pressure Regulator
3. Direct Ignition System Module
4. Engine Harness Ground
5. Camshaft Position (CMP) Sensor
6. Oil Pressure Switch
7. R.H. Knock Sensor (KS)
8. Vehicle Speed Sensor (VSS) Automatic Trans)
9. Injectors (3 places)
9
8
76
4201
5
4
31
2
Figure 6C2-1-7 – V6 Supercharged Engine, Automatic Transmission, Internal Electronic Component Locations
Legend
1. Vehicle Speed Sensor
2. 1-2 Shift Solenoid A and 2-3 Shift Solenoid B
3. Automatic Transmission Fluid Pressure (TFP)
Manual Valve Position Switch
4. 3-2 Downshift Control Solenoid
5. Torque Converter Clutch Pulse Width Modulation (TCC
PWM) Solenoid Valve
6. Torque Converter Clutch (TCC) Solenoid Valve
7. Pressure Control Solenoid (PCS) Valve
1.1 POWERTRAIN CONTROL MODULE
The Powertrain Control Module (PCM) (1) is
mounted to a bracket (2), located behind the front
left hand cowl trim panel (3) and is the control
centre of the engine and transmission management
systems. It constantly monitors information from
various sensors, and controls the systems that
affect exhaust emissions and vehicle performance.
The PCM performs the diagnostic function of the
system. It can recognise operational problems,
alert the driver through a
"Check Powertrain" Malfunction Indicator
Lamp (MIL) display and store a diagnostic code(s)
that will identify problem areas to aid the
technician in making repairs. Refer to
Section 6C2-2 DIAGNOSIS for more information
on using the diagnostic functions of the PCM.
The PCM s upplies either a buff ered 5 or 12 volts to
power various sensors or switches. This is done
through resistances in the PCM which are so high
in value that a test light will not light when
connected to the circuit.
In some cases, even an ordinary voltmeter will not
give an accurate reading because the meter's
internal resistance is too low.
NOTE: A 10 Megohm input impedance digital
voltmeter is required to assure accurate voltage
readings.
Figure 6C2-1-8 – Powertrain Control Module Location
The PCM c ontrols output c irc uits suc h as the inj ec tors , IAC, and var ious r elays, etc. by controlling the ground circuit
through transistors or a device located in the PCM called a "Quad-Driver" module (QDM). Two exceptions to this
are the fuel pump relay control circuit and the automatic transmission Pressure Control Solenoid (PCS).
The fuel pump relay is the only PCM controlled circuit where the PCM controls the +12 volts sent to the coil of the
relay. The ground side of the f uel pump relay coil is connected to engine ground. T he PCM supplies current to the
PCS and monitors how much current returns to the PCM on a separate terminal.
PCM SECURITY LINK
Once the PCM and/or BCM have been r eplaced, the new PCM and/or BCM mus t be s ecur ity linked to each other. If
this procedure is not performed, the vehicle will not crank. Refer 2.1 POWERTRAIN CONTROL MODULE, PCM
SECURITY LINK, in Section 6C2-3 SERVICE OPERATIONS.
PROGRAMMABLE READ ONLY MEMORY (PRO M)
To allow one model of PCM to be used for many
diff erent vehicles, a device called a PRO M is used.
The PROM is located inside the PCM and has
information on the vehicle's weight, engine,
transmission, axle ratio and several other factors.
While one PCM part number m ay be used by many
different vehicles, a PROM is specific. For this
reason, it is ver y im portant to chec k the latest parts
catalogue and Technical Information Bulletins for
the correct part number when replacing a PROM.
A replacement PCM (called a controller) (1) is
supplied without a PROM (2). After removing the
cover (3), the PROM from the old PCM must be
carefully removed and installed in the new PCM.
For details, refer Section 6C2-3 SERVICE
OPERA TIONS in this Service Information.
3
4204
2
1
Figure 6C2-1-9 – PROM Location
PCM MEMORY FUNCTIONS
There are three types of memory storage within the PCM: RAM, EPROM and EEPROM.
RAM
Random Access Memory (RAM) is the microprocessor "scratch pad." The processor can write into, or read from
this memory as needed. This memory is volatile and needs a constant supply of voltage to be retained. If the
voltage is lost, the memory is lost.
EPROM
Erasable Programmable Read Only Memory (EPROM) is the portion of the PCM which means that the program can
be erased. This is also the portion of the PCM that contains software and the different engine and transmission
calibration inform ation that is specific to year, model and em issions. This memory is erased by exposing it to high
intensity ultra violet radiation for several minutes.
The service Programmable Read Only Memory (PROM) which is used by technicians in the field to update
calibrations in the PCM is actually an EPROM. T he service PROM is removable f rom the PCM. The PROM should
be retained with the vehicle following PCM replacement.
EEPROM
Electrically Erasable Programmable Read Only Memory (EEPROM) is the portion of the PCM that means the
program can only be erased electronically. This type of memory cannot be erased by disconnecting the vehicle's
battery. The only way to erase this type of memor y is by a spec ial elec tronic tool, s uch as the Tech 2 s c an tool. This
type of m emory is used to store the Diagnostic Trouble Codes (DT C). DTC history data is stored in EEPROM and
will be saved even after the vehicle's battery has been disconnected. For this reason, the only way that the DTC
history data can be cleared is with the Tech 2 scan tool.
1.2 ENGINE INFORMATION SENSORS AND SIGNALS
CAMSHA FT POSITION SENSOR (CMP)
The camshaft position (CMP) sensor (1) is located
in the engine front cover, behind and below the
water pump, near the camshaft sprocket.
As the cam shaf t spr ock et turns, a m agnet mounted
on it activates the Hall Ef f ec t s witch in the c amshaft
position sensor (1). When the Hall Effect switch is
activated, it ground's the signal line to the DIS
module, pulling the camshaft position signal line's
applied voltage low. This is interpreted as a
camshaft position signal (Synchronisation Pulse).
Because of the way the signal is created by the
camshaft position sensor, the signal circuit is
always either at a high or low voltage (digital
signal).
While the camshaft sprocket continues to turn, the
Hall Eff ect switch turns "OFF" as the m agnetic f ield
passes the camshaft position sensor, resulting in
one signal each time the camshaft makes one
revolution.
The camshaft position signal, which actually
represents camshaft position due to the sensor's
mounting location, is used by the PCM to properly
time its sequential fuel injection operation.
1
4205
Figure 6C2-1-10 – Camshaft Position (CMP) Sensor
Figure 6C2-1-11 – Camshaft and Crankshaft Position Sensor Locations
Legend
1. Camshaft Sprocket
2. Magnetic Interrupter
3. Front Cover
4. Camshaft Position (CMP) Sensor
5. Crankshaft Position (CKP) Sensor
Camshaft Position Signal
The PCM uses the cam shaft position signal to determine the position of the No. 1 piston on its power strok e. This
signal is used by the PCM to calculate sequential f uel inj ec tion oper ation. If the c amshaft position s ignal is los t while
the engine is running, the fuel injection mode will be based on the last fuel injection pulse, and the engine will
continue to run. The engine can be restarted and will run in sequential mode, even though the fault is present.
When the camshaft position signal is not received by the PCM, DTC 48 will be set.
If the PCM sees an incorrect number of pulses on the Camshaft Position PCM input circuit, DTC 49 will set.
If either of thes e DTC's ar e s et, the f uel system will rem ain in sequential fuel injection mode. However, the PCM has
a one in six chance of sequencing the injectors at the ideal time in the engine cycle.
Figure 6C2-1-12 – Camshaft Position Signal
Legend
1. Camshaft Position (CMP) Sensor
2. Camshaft Gear 3. Magnetic Interrupter
4. Camshaft Position Signal = One Camshaft Rotation
The Camshaft Position signal is a normally high signal that will go low for 60° once every 720° of crankshaft
rotation. T he timing of the cams haft signal is not c ritical sinc e it only provides inform ation to the PCM for sequential
fuelling.
DTC 48 (Camshaft Position Sensor Circuit Low Voltage) will set if:
• The engine is running.
• The PCM detects the Camshaft Position sensor signal is low when the signal should be high for 5.0 seconds.
• The PCM will not illuminate the Check Powertrain MIL.
DTC 49 (Camshaft Position Sensor Circuit Performance) will set if:
• The engine is running.
• An incorrect number of crankshaft reference pulses have been received since the previous camshaft position
signal.
• The PCM will not illuminate the Check Powertrain MIL.
Default Value
If either DTC is set, the PCM will determine the fuel injection sequence based on the last fuel injection pulse
received. In the calculated SFI mode, the engine continues to start and run. However, with the fault present, only a 1
in 6 chance of the correct injection sequence exists.
Recovery will occur on the next ignition cycle.
DTC 48 AND 49 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED BATTERY VOLTAGE
TIME FROM START REFERENCE VOLTAGE
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES INJECTOR VOLTAGE
COOLANT TEMPERATURE
Figure 6C2-1-13 – Camshaft Position Signal
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
The Engine Coolant Temperature (ECT) sensor is a
thermistor (a resistor that changes value based on
temperature) mounted in the engine coolant stream
and is used by the PCM and other control modules
via the serial data bus f or engine coolant temperature
information. Low engine coolant temperature
produces a high sensor resistance (28,939 ohms at -
20° C) while high engine coolant temperature causes
low sensor resistance (180 ohms at 100° C).
Figure 6C2-1-14 – ECT Sensor
The Engine Coolant Temperature sensor location on
the V6 Supercharged engine is at the rear of the
engine.
Legend
1. Engine Coolant Temperature (ECT) Sensor
2. Locking Tang
3. Wiring Harness Connector
Figure 6C2-1-15 – ECT Sensor Location
The PCM supplies a 5 Volt signal to the engine
coolant tem per ature ( ECT) s ensor, either through two
resistors in series or through just one of these two
resistors. When the engine coolant is cold, the PCM
monitors the sensor voltage through two resistors in
series with one another and then switches one
resistor out of the circuit at approx imately 50° C. This
switching is shown by points ‘A’ (sensor just below
50° C) and point ‘B’ (sensor just above 50° C).
The circuit voltage will vary depending on the
resistance of the engine coolant temperature sensor.
The circuit voltage will be close to the 5 volt level
when the sensor is cold, and will decrease as the
sensor warms. Engine coolant temperature affects
most systems controlled by the PCM.
A failure in the engine coolant temperature sensor
circuit should set either DTC 14 or DTC 15.
An interm ittent open or a short f ailure should s et DTC
16.
W hile the circuit voltage will change at approximately
50° C, the Tech 2 scan tool will still read the correct
temperature value and will not suddenly jump (as
indicated f rom points ‘A’ to ‘B’). A failur e in one of the
two resistors should set DTC 17.
Figure 6C2-1-16 – ECT Temperature (T) vs Voltage (V)
DTC 14 (Engine Coolant Temperature (ECT) Sensor Low Voltage) will set if:
• Engine run time is longer than 10 seconds.
• The ECT sensor signal indicates an engine coolant temperature greater than 134°C.
• Above conditions present for at least 10 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 15 (Engine Coolant Temperature (ECT) Sensor High Voltage) will set if:
• Engine run time is longer than 10 seconds.
• The ECT sensor signal indicates an engine coolant temperature less than -30°C.
• Above conditions present for at least 1 second.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 16 (Engine Coolant Temperature (ECT) Signal Voltage Unstable) will set if:
• Engine run time is longer than 10 seconds.
• The ECT sensor reading changes more than 400 mV in 200 milliseconds.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
DTC 17 (Engine Coolant Temperature (ECT) pull-up Resistor Failure) will set if:
• Engine run time is longer than 10 seconds.
• The pull-up resistor inside the PCM switches and there is less than a 60mV change in the engine coolant
temperature signal.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
When an ECT sensor circuit fault is detected, and current, the PCM will substitute a coolant temperature default
value. The PCM arr ives at this def ault, or s ubstitute value, by switching to a star ting point, then counting upwards to
95° C at a rate of 11 degrees per minute.
The starting point is the present temperature indication from the Intake Air Temperature (IAT) Sensor.
NOTE: W hen a DTC 14, 15, 16 or 17 is current, the PCM will turn on the electric engine cooling fan(s). This is a
FAIL-SAFE action by the PCM to prevent a possible engine overheat condition, since these DTC’s indicate an
unknown actual engine coolant temperature.
If the ECT s ens or c irc uit opens with the ignition off , the PCM will interpret - 30° C and deliver enough f uel to s tar t the
engine at this temperature. If the actual ambient temperature is above 0°C, the engine may flood and not start
unless CLEAR FLOOD MODE is used by fully depressing the accelerator while cranking. In the CLEAR FLOOD
MODE the injectors pulse width is set to zero milliseconds.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 14, 15, 16 AND 17 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED IAT SENSOR
TIME FROM START INTAKE AIR TEMPERATURE
TIMES OCCURRED BATTERY VOLTAGE
IGNITION CYCLES REFERENCE VOLTS
ECT SENSOR
Figure 6C2-1-17 ECT Sensor Circuit
EXHAUST GAS OXYGEN SENSOR
The exhaust gas oxygen sensors are the key to
fuel control. The PCM uses information from the
oxygen sensors to precisely fine-tune its fuel
injector pulse width calculations, based on the
unused, "left-over" oxygen content in the exhaust.
The V6 Supercharged engine uses two heated
oxygen sensors, with one oxygen sensor located in
each exhaust pipe. This is done so that the PCM
can better control the engine's fuelling
requirements. These heated oxygen sensors have
an internal heater element (2) that is used to heat
the Zirconia element (8) faster inside the sensors,
thereby decreasing the amount of time the fuel
control system needs before running in closed loop
fuel control.
These oxygen sensors have a zirconia element (8)
that, when heated to temperatures above 360° C,
produce voltages based on the amount of oxygen
content s urr ounding the tip, as compar ed to oxygen
in the atmosphere.
The s ensor is m ounted in the exhaust pipe with the
sensing portion exposed to the exhaust gas
stream. When the sensor has reached an operating
temperature of more than 360° C, it acts as a
voltage generator, producing a rapidly changing
voltage of between 10 - 1000 millivolts.
Legend:
1. Lower Shield
2. Heater Element
3. Body
4. Lead Seal
5. Upper Shield
6. Seal Gasket
7. Outer Electrode and Protective Coating
8. Zirconia Element
9. Inner Electrode
Figure 6C2-1-18 Four Wire Heated Oxygen Sensor
This voltage output is dependent upon the oxygen content in the exhaust gas, as compared to the sensor's
atmospheric oxygen reference cavity. The reference cavity of this heated oxygen sensor is exposed to the
atmos pher e by the air that pas s es between the wire strands and ins ulation. T he s ignal and heater leads us ed of the
heated oxygen sensor are of the s tranded type that have small s paces between the wire strands and the insulation.
Thes e spaces allow a satisfac tory am ount of air to pass thr ough the lead to m aintain an adequate air referenc e f or
the sensor.
IMPORTANT: Under no circumstances are the wiring harness connectors associated with the heated oxygen
sensor circuits to be sealed in any way, by using grease or other substance. To do so, would result in an inadequate
supply of referenc e air to be able to r eac h the atmospher ic r ef er ence c avity of each sens or, r es ulting in a DTC to be
set. If a f lexible s ealant is used (i.e. gr ease), then this would be drawn into the sensor cavity, poisoning the s ensor,
resulting in a premature failure. Also, should connector damage be evident, then the sensor and lead must be
replaced, as soldering of the wiring would also negate the ‘breathing’ capability of the sensor wiring.
When the sensor is cold, it produces either no voltage, or an unusable, slowly changing one. Also when cold, its
internal electric al r es istanc e is ex tremely high - many million ohms . The PCM always supplies a steady 450 millivolt,
very low current, "bias" voltage to the oxygen sensor circuit. When the sensor is cold and not producing any voltage,
the PCM "detec ts " only this s teady bias voltage. As the sens or begins heating, its internal r es istanc e dec reas es and
it begins producing a rapidly changing voltage that will overshadow the PCM's supplied steady bias voltage.
When the PCM "detects" the changing voltage, it
knows the oxygen sensor is hot and its output
voltage can be used for "fine-tuning" the fuel
injector puls e width. T he PCM monitors the oxygen
sensor's "changing voltage" for going above and
below a mid-range voltage band (approximately
300 - 600 m illivolts ), to help decide when to operate
in the closed-loop mode. (refer "B’ (Ready Test),
Figure 6C2-1-21.)
When the fuel system is correctly operating in the
closed-loop mode, the oxygen sensor voltage
output will change rapidly, several times per
second, going above and below a rich/lean band.
The PCM monitors the changing voltage, and
decides the needed fuel mixture correction. (refer
"A’ (Normal, Closed-Loop Operation), Figure 6C2-
20).
An open s ensor s ignal circuit or gr ound circuit, or a
defective, contaminated, or cold sensor could
cause the voltage to stay within a 350-550 millivolt
band too long, keeping the fuel control system in
open-loop and setting either DTC 13 or DTC 63.
Legend:
A. More Conduction (Exhaust Gas with 0% Oxygen)
B. Less Conduction (Exhaust Gas with 2% Oxygen)
1. Atmospheric Reference Cavity
Figure 6C2-1-19 Oxygen Sensor Zirconia Element
If the PCM monitors a low voltage for too long (indicating a "lean" exhaust), either DTC 44 or DTC 64 will set.
If the PCM m onitors a high oxygen sensor c ircuit voltage for too long ( indicating a "rich" exhaus t), either DTC 45 or
DTC 65 will set.
Response Time
Not only is it necessary for the oxygen sensor to produce a voltage signal for rich or lean exhaust, it is also
impor tant to r espond quic kly to changes. The PCM s ens es the r es ponse times and dis plays this on the Tech 2 scan
tool as the "rich-lean status" and as "cross counts". If the oxygen sensor responds slowly, the customer may
complain of poor fuel economy, rough idle or lack of performance. It may also set false PCM DTC’s because the
PCM uses oxygen sensor voltages for system checks.
Oxygen Sensor Contaminants
Carbon
Black carbon or soot deposits result from over-rich air/fuel mixtures. However, carbon does not harm an oxygen
sensor. Deposits can be burned off in the vehicle by running it at least part throttle for two minutes.
Silica
Certain RTV silicone gasket materials give off vapour as they cure that may contaminate the oxygen sensor. This
contamination is usually caused by the vapours being pulled from the PCV system, into the combustion chamber
and passed on to the exhaust system. The sand like particles from the RTV silica embed in the molecules of the
oxygen sensor element and plug up the surface. W ith the outside of the oxygen sensor element not able to sense
all of the oxygen in the exhaust s ystem it results in "lazy" oxygen sensor res ponse and engine control. The ox ygen
sensor will have a whitish appearance on the outside if it has been contaminated.
There is also a possibility of silica contamination caused by silicone in the fuel. Some oil companies have used
silicone to raise the octane rating of their fuel. Careless fuel handling practices with transport containers can result
in unacceptable concentrations of silicone in the fuel at the pump.
There is also a possibility of silica contamination caused by silicon in lubricants used to install vacuum hoses on
fittings. Do not use silicone sealers on gaskets or exhaust joints.
Lead
Lead glazing of the sensors can be introduced when regular, or leaded fuel is burned. Fuel containing large
amounts of methanol will also result in lead contamination.
The methanol dissolves the terne coating of the fuel tank, which introduces lead into the fuel system, and into the
exhaust after combustion. It is difficult to detect lead contamination by visual inspection.
Other Substances
Oil deposits will ultimately prevent oxygen sensor operation. The sensor will have a dark brown appearance.
Causes of high oil consumption should be checked.
The additives in ethylene glycol can also af fec t oxygen sensor perf orm anc e. This produces a whitish appearance. If
antifreeze enters the exhaust system, you will likely encounter other, more obvious, symptoms of cooling system
trouble. If for example the engine had a head gasket failure where coolant did enter the combustion chamber it
would be a good idea to check the oxygen sensor operation after the head gasket was repaired.
Multiple Failures
Leaded fuel, silic a contam ination f rom uncur ed, low-grade (unapproved) RTV s ealant, and high oil consum ption are
possible causes.
Figure 6C2-20 Oxygen Sensor Voltage Curves
Legend
A. Normal, Closed Loop Operation
B. Lean – Below 200 mV for too long in Closed Loop (DTC 44 or 64 Will Set)
C. Rich – Above 780 mV for too long in Closed Loop (DTC 45 or 65 Will Set).
D. Between 410 – 477 mV Too Long (DTC 13 or 63 Will Set).
800 mV – Rich
450 mV – PCM O2 Reference Signal
200 mV – Lean
Figure 6C2-1-21 Normal Oxygen Sensor Voltages, and Abnormal Trends
Legend
A. More than 780 mV for Too Long (plus other parameters). (DTC 45 or 65 Will Set)
B. “Ready” Test
C. Less than 200 mV for Too Long (plus other parameters). (DTC 44 or 64 Will Set)
D. Between 410 and 477 mV (DTC 13 or 63 Will Set)
E. Rich-Lean Band at a Hot Idle (between 490 and 500 mV)
DTC 13 (RH Oxygen Sensor Insufficient Activity) will set if:
• No TP Sensor DTC’s are set.
• The ECT sensor is more than 85°C.
• TP Sensor voltage indicates the throttle is open more than 15%.
• RH O2S voltage stays between 410-477 millivolts.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 44 (RH Oxygen Sensor Lean Exhaust Indicated) will set if:
• No IAT Sensor DTC’s are set.
• RH O2S signal voltage remains below 200 millivolts for 46 seconds.
• The system is in “Closed Loop”.
• IAT Sensor is below 75°C.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 45 (RH Oxygen Sensor Rich Exhaust Indicated) will set if:
• No TP Sensor DTC’s are set.
• RH O2S signal voltage remains above 780 millivolts for 40 seconds.
• The system is in “Closed Loop”.
• Throttle angle is between 9% and 30%.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
Once an O2S DTC is set and current, the PCM will operate the fuel system in the “Open Loop” mode.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 13, 44, AND 45 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED MASS AIR FLOW
TIME FROM START R.H SHORT TERM FUEL TRIM
TIMES OCCURRED R.H LONG TERM FUEL TRIM
IGNITION CYCLES THROTTLE ANGLE
R.H O2 SENSOR
DTC 63 (LH Oxygen Sensor Insufficient Activity) will set if:
• No TP Sensor DTC’s are set.
• The ECT sensor is more than 85°C.
• TP Sensor voltage indicates the throttle is open more than 15%.
• LH O2S voltage stays between 410-477 millivolts.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 64 (LH Oxygen Sensor Lean Exhaust Indicated) will set if:
• No IAT Sensor DTC’s are set.
• LH O2S signal voltage remains below 200 millivolts for 46 seconds.
• The system is in “Closed Loop”.
• IAT Sensor is below 75°C.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 65 (LH Oxygen Sensor Rich Exhaust Indicated) will set if:
• No TP Sensor DTC’s are set.
• LH O2S signal voltage remains above 780 millivolts for 40 seconds.
• The system is in “Closed Loop”.
• Throttle angle is between 9% and 30%.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
Once an O2S DTC is set, and current, the PCM will operate the fuel system in the “Open Loop” mode.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 63, 64, AND 65 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED L.H O2 SENSOR
TIME FROM START MASS AIR FLOW
TIMES OCCURRED L.H STFT
IGNITION CYCLES L.H LTFT
COOLANT TEMPERATURE THROTTLE ANGLE
Figure 6C2-1-22 V6 Supercharged Engine Four Wire Oxygen Sensor Circuit
INTAKE AIR TEMPERATURE (IAT) SENSOR
The Intake Air Temperature (IAT) sensor is a thermistor (a resistor that changes resistance with changes in
temperature) mounted in the air cleaner housing of the intake system. Low intake air temperature produces high
resistanc e in the sensor (100,866 ohm s at -40° C), while high intake air tem perature caus es low sensor resistanc e
(78 ohms at 130° C).
The PCM:
1. Supplies a 5 volt signal voltage to the sensor through a resistor in the PCM, and
2. Monitors the intake air temperature circuit voltage, which will change when connected to the intake air
temperature sensor.
The circuit voltage will vary depending on the resistance of the IAT sensor. The voltage will be close to the 5 volt
level when the sensor is cold, and will decrease as the sensor warms.
The input intake air temperature signal voltage is used by the PCM to assist in calculating the fuel injector pulse
width.
A failure in the IAT sensor circuit should set either DTC 23 or 25.
An intermittent or unstable voltage in the IAT sensor circuit should set DTC 26.
Figure 6C2-1-23 – IAT Sensor & Location
Legend
1. Wiring Harness Connector
2. Air Cleaner Upper Housing
3. Mating Tang
4. Retainer
5. IAT Sensor
DTC 23 (Intake Air Temperature Sensor Signal Voltage High) will set if:
• IAT Sensor signal voltage is more than 4.9 volts, indicating an intake air temperature below –36°C for more
than one second.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
DTC 25 (Intake Air Temperature Sensor Signal Voltage low) will set if:
• IAT Sens or signal voltage is les s than 0.3 volts , indicating an intake air tem perature above 147°C for m or e than
one second.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
DTC 26 (Intake Air Temperature Sensor Unstable Voltage) will set if:
• Engine run time is longer than 10 seconds.
• IAT Sensor reading changes more than 140 millivolts in 100 milliseconds
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Value
Once an IAT DTC is set and current, the PCM will substitute an IAT value of 25°C.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 23, 25 AND 26 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED ECT SENSOR
TIME FROM START IAT SENSOR
TIMES OCCURRED BATTERY VOLTAGE
IGNITION CYCLES REFERENCE VOLTS
COOLANT TEMPERATURE
Figure 6C2-1-24 IAT Sensor Circuit
MASS AIR FLOW (MAF) SENSOR
The Mass Air Flow (MAF) sensor (1) used on this engine, utilises a heated element type of operation. A heated
element in the MAF is placed in the air flow str eam of the engine intak e s ystem. T he heating elem ent is m aintained
at a constant temperature differential above the air temperature. The amount of electrical current required to
maintain the heated elem ent at the proper temperature is a direct function of the mass flow rate of the air past the
heated element.
Figure 6C2-1-25 – Mass Air Flow Sensor & Location
Three sensing elements are used in this system.
One senses ambient air temperature (1) and uses
two calibratable resistors (2) to establish a voltage
that is always a function of ambient temperature.
This am bient sensor is m ounted in the lower half of
the sensor housing. The other two sensing
elements are heated to a predetermined
temperature that is significantly above ambient air
temperature.
The two heated elements (2) are connected
electric ally in par allel and m ounted direct ly in the air
flow stream of the sensor housing. One element is
in the top and the other elem ent is in the bottom of
the sensor housing. This is done so that the air
meter is less sensitive to upstream ducting
configurations that could skew the flow of air
through the housing.
As air passes over the heated elements during
engine operation they begin to cool. By measuring
the amount of elec tr ical c ur rent r equir ed to maintain
the heated elements at the predetermined
temperature above ambient temperature the mass
air flow rate can be determined.
Once the mass air flow sensor has developed an
internal signal related to the mass air flow rate, it
must send this information to the PCM. In order to
preserve the accuracy and resolution of the small
voltage signal in the mass air flow sensor, it is
converted to a frequency signal by a voltage
oscillator and sent to the PCM.
Figure 6C2-1-26 Sensing Elements
Figure 6C2-1-27 – MAF Sensor Simplified Schematic
The s ignal that is s ent f r om the mass air flow sensor is s ent in the f orm of a frequenc y output. A large quantity of air
passing through the sensor (such as when accelerating) will be indicated as a high frequency output. A small
quantity of air pass ing through the sens or will be indicated as a low fr equency output (such as when decelerating or
at idle). T he Tec h 2 scan tool dis plays MAF sensor inf orm ation in f requenc y, in grams per second (calc ulated in mg
per cylinder). At idle, the readings should be low and increase with engine RPM.
As the PCM r ec eives this f r equenc y signal from the Mass Air F low sensor , it s earc hes its pr e- progr ammed tables of
information to determine the pulse width of the fuel injectors required to match the Mass Air Flow signal.
If a problem occurs in the Mass Air Flow sensor circuit, after a period of time, the PCM will store a DTC in its
memory. The PCM will turn "ON" the "Check Powertrain" Malfunction indicator Lamp (MIL) indicating there is a
problem. If this occurs, the PCM will calculate a "substitute" Mass Air Flow signal based on engine speed and
Throttle Position (TP) sensor signal.
No field service adjustment is necessary or possible with this Mass Air Flow sensor.
A failure in the Mass Air Flow sensor circuit should set DTC 32.
Remember, this DTC indicates a failure in the circuit, so proper use of the diagnostic Table will lead to either
repairing a wiring problem or replacing the MAF Sensor, to properly repair a problem.
The Mas s Air Flow sensor identification is m ade up
of four number groups:
Legend:
1. Year
2. Julian Date (Day of the Year)
3. Last Four Digits of Part Number.
4. Flow Stand Number.
Figure 6C2-1-28 – Mass Air Flow Sensor Identification
DTC 32 (Mass Air Flow System Performance) will set if:
• The engine is running.
• No MAF Signal for over two seconds.
• Above conditions present for at least 10 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
W hen a MAF sens or or circuit f ault is detected, and current, the PCM will subs titute a MAF sensor value based on
RPM, throttle angle and IAC position.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 32 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED R.H O2 SENSOR
TIME FROM START MASS AIR FLOW
TIMES OCCURRED R.H STFT
IGNITION CYCLES R.H LTFT
COOLANT TEMPERATURE THROTTLE ANGLE
Figure 6C2-1-29 – MAF Sensor Circuit
THROTTLE POSITION (TP) SENSOR
The Throttle Position (TP) sensor is connected to
the throttle shaft on the throttle body unit. It is a
potentiometer with one end connected to 5 volts
from the PCM and the other end to PCM ground. A
third wire connects from a sliding contact in the T P
sensor to the PCM allowing the PCM to measure
the voltage from the TP sensor.
As the throttle is m oved (ac celerator pedal moved) ,
the output of the TP sensor changes. At a closed
throttle position, the output of the TP sensor is
below 1.25V. As the throttle valve opens, the output
increases so that, at wide-open throttle (W OT ), the
output voltage should be about 4 volts.
By monitoring the output voltage from the TP
sensor, the PCM c an determ ine fuel delivery based
on throttle valve angle (driver demand). A broken or
loose TP sensor can cause intermittent bursts of
fuel from the injectors, and an unstable idle,
because the PCM interprets the throttle is moving.
Figure 6C2-1-30 – TP Sensor
The TP s ensor (2) is not adjustable and there is no
set value for voltage at closed throttle, becaus e the
actual voltage at closed throttle can vary from
vehicle to vehicle due to tolerances. The PCM has
a special progr am built into it that can adjus t for the
tolerances in the TP sensor voltage reading at idle.
The PCM us es the r eading at c losed thr ottle idle for
the zero reading (0% throttle) so no adjustment is
necessary. Even if the TP sensor voltage reading
was to be changed by; tampering, throttle body
coking, sticking cable or any other reason, the TP
sensor will s till be 0%. The PCM will learn what the
closed throttle value is every time the throttle
comes back to closed throttle. The new closed
throttle value will be used by the PCM and no
driveability complaint will be present because the
PCM learned a new setting.
A failure in the TP sensor circuit should set either
DTC 21 or 22. If the internal spring in the TP
sensor s hould fail, the T P sens or will be stuck high.
A sticking TP sensor should set DTC 19.
Legend
1. Idle Air Control (IAC) Valve
2. Throttle Position (TP) Sensor
3. Throttle Body
Figure 6C2-1-31 – TP Sensor Location
DTC 19 (Throttle Position Sensor Stuck) will set if:
• The TP Sensor indicated percentage of opening is greater than the RPM that can be reached with a Mass Air
Flow of less than 301 mg/cyl.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 21 (Throttle Position Sensor Signal Voltage High) will set if:
• The TP Sensor voltage between the PCM TP Sensor signal terminal and the TP Sensor ground terminal is
greater than 4.9 volts for more than two seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 22 (Throttle Position Sensor Signal Voltage Low) will set if:
• The T P Sensor voltage between the PCM TP Sensor s ignal term inal and the T P Sensor ground term inal is less
than 0.2 volts for more than two seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
Once a TP Sensor DTC is set, and current, the PCM will substitute a TP Sensor value based on Idle Air Control
Valve position and Mass Air Flow.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 19, 21, AND 22 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED TP SIGNAL
TIME FROM START MASS AIR FLOW
TIMES OCCURRED R.H LTFT
IGNITION CYCLES BATTERY VOLTAGE
COOLANT TEMPERATURE REFERENCE VOLTS
Figure 6C2-1-32 – TP Sensor Circuit
VEHICLE SPEED SENSOR (VSS)
The VSS (1) provides an indication of road speed to the PCM. The sensor is mounted in the extension housing of
the transmission and is an inductive pick-up or pulse generator, which generates an AC voltage at a varying
frequency. The frequency will change with a change in output shaft speed. The PCM uses this signal for internal
processing and to also generate a vehicle speed signal for use by other control modules
The PCM als o uses inf orm ation f rom the VSS f or IAC valve operation and some of the engine fuelling modes. If the
PCM receives no pulses on the vehicle speed sensor input while certain conditions exist, DTC 24 will be set.
DTC 24 will set if a fault exists in the vehicle speed sensor circuit when the vehicle is accelerated, and the VSS
signal is constant, or not pulsing. The DTC will set and a default value will be substituted by the PCM. As long as
the fault remains and the diagnostic trouble code is set. If the fault is removed, norm al operation will resume after
the next ignition cycle.
The vehicle speed sensor contains a coil that has a continuous magnetic field, generated by the magnetic pick-up
(3). A voltage signal is induced in the vehicle speed sensor by teeth on the output shaft (4) that rotate past the
sensor and br eak the m agnetic field. Each break in the field sends an electr ical pulse from the electrical connector
(2) and wiring harness, to the PCM.
The O-ring (5), prevents transmission fluid from leaking externally.
Figure 6C2-1-33 – Vehicle Speed Sensor & Location
Legend
1. Vehicle Speed Sensor
2. Electrical Connector
3. Magnetic Pickup
4. Rotor
5. O-Ring
This voltage output will vary with transmission output shaft speed from a minimum of 0.5 volts AC at 100 RPM to
more than 100 volts AC at 8000 RPM with no load on the circuit on the vehicle, with the engine at 4,000 RPM in
fourth gear the voltage will be approximately 10-12 volts AC.
The PCM uses speed information from this sensor to determine the following:
• Vehicle speed.
• Control shift points (Auto Trans).
• Calculate transmission slip (Auto Trans).
• Engine fuelling modes.
DTC 24 will set if a f ault ex is ts in the vehicle s peed s ensor c irc uit indic ating the vehicle is not moving. As the vehicle
is accelerated, the PCM shifts the transmission to second gear at approximately 3,000 RPM. If the vehicle speed
signal is still not pres ent while in second gear, the DT C is set, the transm iss ion will have maxim um line pressure in
2nd gear only and have no TCC. A default value will be substituted by the PCM.
DTC 72 will set if there is an intermittent failure in the VSS circuit while the vehicle is moving. As long as the fault
remains and DTC 72 is set, the PCM will have maximum line pressure and 3rd gear only. If the fault is removed,
normal operation will resume after the next ignition cycle.
DTC 24 (Vehicle Speed Sensor Circuit Low Voltage) will set if:
• The transmission is not in Park or Neutral.
• The engine speed is greater than 3000 RPM.
• The TP Sensor angle is between 10% and 99%.
• The VSS indicates an output shaft speed of less than 3 km/h for 3 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
When the DTC sets, the PCM will command second gear only, maximum line pressure, freeze shift adapts from
being updated and inhibit TCC engagement.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 24 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED THROTTLE ANGLE
TIME FROM START TFT
TIMES OCCURRED MASS AIR FLOW
IGNITION CYCLES COMMANDED GEAR
COOLANT TEMPERATURE VEHICLE SPEED
DTC 72 (Output Speed Loss) will set if:
• The transmission is not in Park or Neutral.
• Two succes sive speed readings have a dif ference of m ore than 1000 RPM in any drive range (differ ence must
be more than 2048 RPM in park or neutral). This test checks the vehicle speed sensor signal to the PCM.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Value
When Diagnostic Trouble Code 72 is set, the transmission will have maximum line pressure and command 3rd gear
only. If DTC 72 is set while in 4th gear, the vehicle will stay in 4th gear. However, as the vehicle is coasting to a
stop, the transmission will downshift normally from 4 to 3. Once the downshift into 3rd gear has occurred, the
vehicle will stay in 3rd gear.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 72 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED TRANSMISSION SLIP SPEED
TIME FROM START TFT
TIMES OCCURRED THROTTLE ANGLE
IGNITION CYCLES VEHICLE SPEED
COOLANT TEMPERATURE COMMANDED GEAR
Figure 6C2-1-34 VSS Circuit
A/C REQUEST SIGNAL
If the vehicle is equipped with HVAC Occupant Clim ate Control (Auto A/C), the HVAC control m odule receives the
command to switch the A/C on and sends this as an A/C request to the PCM, via the serial data bus.
W hen A/C is reques ted from the dash master A/C switch, the A/C request signal is sent to the BCM. T he BCM will
then send a command via the serial data line to the PCM. The PCM will then supply a ground signal to the A/C
compressor relay, to energise the A/C compressor. There are no PCM DTC(s) associated with this A/C Request
Signal. Refer to Section 6C2-2A DIAGNOSTIC TABLES, table A-11.1 or A 11.3 for A/C system diagnosis.
The PCM uses this serial data command to:
1. Adjust the Idle Air Control (IAC) position to compensate for the additional load placed on the engine by the air
conditioning compressor, and then
2. Energises the A/C compressor relay, to operate the A/C compressor.
Figure 6C2-1-35 HVAC Occupant Climate Control (Automatic A/C)
Figure 6C2-1-36 A/C Request Signal Circuit – HVAC Climate Control (Manual A/C)
BATTERY VOLTAGE
The PCM continually monitors battery voltage. W hen the battery voltage is low, the ignition system may deliver a
weak spark and the injector mechanical movement takes longer to open the injector. The Powertrain Control
Module will compensate by:
1. Increasing the ignition coil dwell time if the battery voltage is less than 12 Volts.
2. Increasing the engine idle RPM if battery voltage drops below 10 Volts.
3. Increasing the injector pulse width if the battery voltage drops below 10 Volts.
W ith vehicles equipped with the V6 Supercharged engine and autom atic trans miss ion, Diagnostic T rouble Code 52
will set when the engine is running and the voltage at PCM terminal “X1 A4” is above 16 Volts for 109 minutes.
Diagnostic Trouble Code (DTC) 53 will set when the ignition is “ON'' and PCM terminal “X1 A4'' voltage is more than
19.5 Volts for about 2 seconds.
Diagnostic Trouble Code (DTC) 54 will set when the ignition is “ON'' and PCM terminal “X1 A4'' voltage changed
more than 2.5 volts in 100 milliseconds.
Diagnostic Tr ouble Code (DT C) 75 will set when the ignition is “ ON'' and PCM ter m inal “X 1 A4'' voltage is les s than
8.6 Volts for about 4 seconds. Minimum voltage allowed for Diagnostic Trouble Code 75 to set is on a graduated
scale and will change with the temperature. Minimum voltage at –40 ° C is 7.3 Volts, minim um voltage at 90° C is
8.6 Volts, minimum voltage at 152 ° C is 11.4 Volts.
DTC 52 (System Voltage Too High – Long Time) will set if:
• The engine is running and the PCM ignition voltage is greater than 16 volts for more than 109 minutes.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
During the time fault is present, the pressure control solenoid is turned "OFF", the transmission shifts immediately to
3rd gear and TCC operation is inhibited.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 53 (System Voltage High) will set if:
• Ignition is on.
• Voltage at PCM ignition feed terminal is more than 19.5 volts for more than 2 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
During the time fault is present, the PCM will turn all transmission output devices off and freeze shift adapts from
being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 54 (System Voltage Unstable) will set if:
• Ignition is on.
• System voltage changes more than 2.5 volts in 100 milliseconds.
• Above conditions present for at least 10 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
There are no default values.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 75 (System Voltage Low) will set if:
• The system voltage is less than 7.3 volts with the TFT at –40° C.
Or:
• The system voltage is less than 10 volts with the TFT at 151° C.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
When DTC 75 sets, the PCM will turn off all transmission output devices and freezes shift adapts from being
updated. T he PCM will also adjust ignition timing and adj ust injector puls e width to com pensate for the low voltage
condition.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 52, 53, 54 AND 75 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED ECT SENSOR
TIME FROM START IAT SENSOR
TIMES OCCURRED BATTERY VOLTAGE
IGNITION CYCLES REFERENCE VOLTS
COOLANT TEMPERATURE
Figure 6C2-1-37 PCM Battery Feed
CRANKSHAFT REFERENCE SIGNAL
The Direct Ignition System (DIS) sends this signal to the PCM to tell it engine RPM and crankshaft position. This
signal is a repeating s eries of low voltage electr ical pulses generated by the ignition module. T he PCM initiates fuel
injector pulses based upon receiving these crankshaft reference signal pulses. If the PCM's MAF sensor input
detects manifold vacuum and the ignition voltage input detects less than 11 volts and there are no crankshaft
reference input pulses, a DTC 46 will set.
This engine also uses the cam shaf t position s ensor s ignal to synchronise the fuel injector circuits for sequential fuel
injection. The PCM also uses these reference pulses for Electronic Spark Timing (EST) operation.
For a full description of the ignition system operation Refer to 1.6 DIRECT IGNITION SYSTEM (DIS) in this Section.
DTC 46 (No Reference Pulses While Cranking) will set if:
• MAF DTC is not set.
• Battery voltage is at or below 11 volts.
• MAF sensor input is above 2048 Hz.
• No DIS reference input pulses at PCM.
• Conditions exist for more than 2 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
There are no def ault values f or the Crank shaft Reference Signal. This DTC is intended to help in diagnosing a no-
start condition.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 46 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED REFERENCE VOLTS
TIME FROM START MASS AIR FLOW
TIMES OCCURRED CAM SIGNAL
IGNITION CYCLES FUELLING MODE
COOLANT TEMPERATURE FUEL PUMP RELAY
BATTERY VOLTAGE
Figure 6C2-1-38 Crankshaft Reference Signal
ENGINE COOLI NG FAN SIGNAL
(Low Speed Operation)
The engine cooling low speed fan is enabled when the low speed relay is energised by the BCM. The PCM will
request the BCM to turn the low speed engine cooling fan relay on or off, via the serial data bus normal mode
message. After the PCM requests a change in the engine cooling fan low speed relay, the BCM will send a
response message back to the PCM via the serial data bus normal mode message confirming it received the
request. A failure in the response communication will set a DTC 92.
There are also two (2) suppression capacitors incorporated into the fan motor wiring circuits. These suppression
capacitors help eliminate fan motor noise through the radio speakers. If these capacitors are open, then noise will
be present through the radio speakers. If shorted to ground, the fan motors could continuously run, or the fuse or
fusible link could fail.
DTC 92 (Low Speed Fan No BCM Response) will set if:
• Engine is idling.
• The PCM sends a request to the BCM to turn on the engine cooling fan low speed relay via the serial data
normal mode message and the BCM does not send a message back to the PCM.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Value
Once DTC 92 is set, the PCM will energise the engine cooling fan high speed relay.
Recovery
Recovery will occur on the next ignition cycle.
DTC 92 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED REFERENCE VOLTS
TIME FROM START MASS AIR FLOW
TIMES OCCURRED CAM SIGNAL
IGNITION CYCLES FUELLING MODE
COOLANT TEMPERATURE FUEL PUMP RELAY
BATTERY VOLTAGE
Figure 6C2-1-39 Engine Cooling Fan Signal Engine Cooling Fan – Low Speed
High Speed Operation
The engine cooling fan high speed is controlled by the PCM based on input from the Engine Coolant T emperature
Sensor (ECT). The PCM will only turn "ON" the engine cooling fan high speed if the engine cooling low speed fan
has been "ON" for 2 seconds and the following conditions are satisfied.
• There is a BCM message response fault which will cause a DTC 92.
• An engine coolant temperature sensor failure is detected, such as DTC 14, 15, 16, 17 or 91.
• Coolant temperature greater than 107° C.
• If the fan low speed was "OFF" when the criteria was met to turn the fan high speed "ON", the fan high speed
will come "ON" 5 seconds after the fan low speed is turned "ON".
• The high speed engine cooling fan relay can also be enabled by the A/C Refrigerant Pressure Sensor input.
The PCM will enable the high speed cooling fan, if the A/C system pressure becomes too high.
There are also two (2) suppression capacitors incorporated into the fan motor wiring circuits. These suppression
capacitors help eliminate fan motor noise through the radio speakers. If these capacitors are open, then noise will
be pres ent through the r adio speakers. Is shorted to ground, the fan m otors could continuous ly run, or the f use or
fusible link could fail.
DTC 91 Quad Driver Module (QDSM) will set if:
• Engine run time is longer than 10 seconds.
• A/C is requested ON.
• The PCM recognises a QDSM malfunction.
• Above conditions present for at least 10 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 91 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED REFERENCE VOLTS
TIME FROM START A/C RELAY
TIMES OCCURRED STARTER RELAY
IGNITION CYCLES PURGE PWM
COOLANT TEMPERATURE HIGH SPEED FAN
BATTERY VOLTAGE ACTUAL TORQUE
Figure 6C2-1-40 Engine Cooling Fan Signal – High Speed
TRANSMISSION POWER/ECONOMY SWITCH
The Power/Economy switch (1) is used to modify
upshifts and shift times. The driver can select either
Economy or Power mode with the switch (1)
located in the centre console.
An animated icon in the instrument cluster Multi
Function Display (MFD) (2) is activated for 2
seconds and then changes to a highlighted “PW R”
icon (3), to remind the driver that the ‘Power Shift’
mode is enabled.
The PCM provides a voltage signal of about 12
volts, and monitors the status of this circuit. In the
Econom y position, the switch is open and the PCM
voltage status signal remains high, about 12 volts.
The PCM does not allow shift point changes in the
economy mode. When the transmission switch is
pressed to the Power position the switch is
momentarily closed and the PCM voltage status
signal is mom entarily pulled low, to about 0.5 volts.
The PCM senses this m omentary voltage drop and
enables Power m ode (alternate shif t pattern tables)
to be utilised.
In the Power mode, the T CC can be applied in 3rd
and 4th gears. When the TCC is applied in 3rd
gear it will stay applied until the normal 4th gear
upshift criteria is m et. W hen the 3-4 ups hift occ urs,
the TCC will be released momentarily. Also, in the
Power mode while in D gear select position, the
PCM will delay the 1-2 and 2-3 shift while under
light throttle. The shift patterns will be the same in
the Econom y and Power m odes if the TP sensor is
between 80% – 100%.
The power mode should be used when towing, as
applying the TCC in 3rd and 4th gear reduces
slippage in the TCC and thus reduces heat build
up.
In cr uise mode oper ation, when the driver activates
the cruise control, the power icon “PWR” and
power mode will be deactivated (if vehicle was in
power mode) and a CRUISE ACTIVE icon will be
displayed in the instrument cluster MFD. The
transmission shift pattern will then switch to cruise
shift pattern.
Figure 6C2-1-41 Transmission Power/Economy Switch
When in cruise mode the PCM will modify the transmission calibration so that transmission shift activity is reduced.
When the key is turned ON, the PCM shift mode is set to the last mode that was previously selected
(Power/Economy). The cruise control is set to OFF at every key ON cycle.
For replacement of the Power/Economy switch, Refer to Section 7C4 AUTOMATIC TRANSMISSION – ON
VEHICLE SERVICE in MY 2003 VY and V2 Series Service Information.
Figure 6C2-1-42 Transmission Power/Economy Switch Wiring
THEFT DETERRENT INPUT
W hen the ignition switch is turned to the “ON” pos ition, the BCM polls the PCM and sends an encr ypted BCM / k ey
security code. The security code is received by the BCM, via the remote key reader (slip ring) or via the remote
receiver in the event of no slip ring communication.
The PCM compares the received security code with its stored security code and if m atched, the PCM will continue
to enable injector fuelling and engine crank.
The PCM will return a Valid Code mes s age (O K TO START ), which tells the BCM to jump fr om the short loop mode
to the long loop mode.
When the ignition switch is turned from the OFF position to the ON position, the BCM will communicate with the
PCM for anti-theft purposes. If the BCM does not receive the message OK TO START from the PCM within 0.5
seconds of the ignition being switched on, the auxiliary bus is isolated via switching within the BCM.
The isolation of the auxiliary data bus during this period eliminates the possibility of a device failure other than the
BCM or PCM causing a problem on the bus and inhibiting anti-theft communications.
This period is known as “Short Loop Time”, and continues until the PCM responds with an acknowledgment or a
maximum of 5 seconds, after which the BCM will switch to the standard poling sequence.
Following successful anti-theft communications, the BCM begins sequential poling of devices on the bus and
normal system operation is established.
DTC 31 will set when the PCM at ignition ON sends 20 messages to the BCM and does not receive a valid theft
deterrent message.
Figure 6C2-1-43 Theft Deterrent System
Legend
1. Remote Receiver Module
2. Remote Coded Key Reader Assembly
3. Code From Remote Coded Key
4. BCM
5. Security Code
6. OK To Start
7. Theft Deterrent Alert Indicator LED (LHS of Instrument)
8. Enable Or Disable Fuel System Control And Starter Motor
9. Powertrain Control Module (PCM)
10. Remote Coded Key
DTC 31 (Theft Deterrent Signal Missing) will set if:
• The ignition is on.
• The PCM sends 20 messages to the BCM and does not receive a valid theft deterrent message.
• Conditions present for at least 10 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Values
There is no default value for DTC 31, the engine will not start if DTC 31 is current.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 31 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED REFERENCE VOLTS
TIME FROM START MASS AIR FLOW
TIMES OCCURRED CAM SIGNAL
IGNITION CYCLES FUELING MODE
COOLANT TEMPERATURE FUEL PUMP RELAY
BATTERY VOLTAGE
Figure 6C2-1-44 Theft Deterrent Serial Data Circuit
OIL PRESSURE SWITCH
The instruments receive oil pressure switch status
information from the PCM via the serial data bus
normal mode message. The PCM monitors the
voltage at terminal X3 E12 to determine the status
of the oil pressure switch. When the oil pressure
switch is open the voltage at X3 E12 will be 12
volts, when the switch closes the voltage at
terminal X3 E12 will be pulled low, less than 0.2
volts via circuit 231 ( Blue wire) and the oil pressur e
switch.
This low voltage is seen by the PCM as an oil
pressur e s witch clos ed input signal. When the PCM
sees this low voltage at terminal X3 E12 the PCM
will command the instruments to activate the oil
pressure warning icon (1), in the MFD. The large
icon and message then revert to the smaller icon
(2). When the PCM sees a high voltage at ter minal
X3 E12 the PCM will command the instruments to
deactivate the oil pressure warning icon, via the
serial data bus normal mode message.
There are no PCM trouble codes for this oil
pressure switch.
Figure 6C2-1-45 – Oil Pressure Warning Lamp
Figure 6C2-1-46 – Oil Pressure Warning Lamp
1.3 AUTOMATIC TRANSMISSION INFORMATION SENSORS & SIGNALS
1-2 (A) AND 2-3 (B) SHIFT SOLENOID VA LVES
IMPORTANT: The shift solenoid valve resistance
should measure 19-24 ohms minimum when
measured at 20° C. The shift solenoid current flow
should not exceed 0.75 amps. The shift solenoid
should energise at a voltage of 7.5 volts or more
(m eas ured ac r oss the ter minals) . The shif t solenoid
should de-energise when the voltage is one volt or
less.
If both solenoids lose power, third gear only results.
The 1-2 and 2-3 shif t solenoid valves (also c alled A
and B solenoids) are identical devices that control
the movement of the 1-2 and 2-3 shift valves (the
3-4 shift valve is not directly controlled by a shift
solenoid). The solenoids are normally open
exhaust valves that work in four combinations to
shift the transmission into different gears.
The PCM energises each solenoid by grounding
the solenoid through an internal quad driver. This
sends current through the coil winding in the
solenoid and moves the internal plunger out of the
exhaust position. When ON, the solenoid redirects
fluid to move a shift valve.
IMPORTANT: The manual valve hydraulically can
override the shift solenoids. Only in D4 do the shift
solenoid states totally determine what gear the
transmission is in. In the other manual valve
positions, the transmission shifts hydraulically and
the shift solenoid states CATCH UP when the
throttle position and the vehicle speed fall into the
correct ranges.
Diagnostic trouble codes 81 and 82 indicate shift
solenoid circuit voltage faults.
The PCM-controlled shift solenoids eliminate the
need for T V and governor pres sures to control shif t
valve operation.
Figure 6C2-1-47 Shift Solenoid
Legend
A Signal Fluid 4 O-Ring
B Exhaust 5 Metering Ball
1 Frame 6 Spring
2 Plunger 7 Connector Terminal
3 Coil Assembly
DTC 81 (2-3 Shift Solenoid Circuit Electrical) will set if:
• The PCM commands the solenoid ON and the voltage input remains high (B+).
• The PCM commands the solenoid OFF and the voltage input remains low (0volts)
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Values
When this DTC sets, the PCM will command D2 line pressure, the PCM will inhibit 3-2 downshift if the vehicle
speed is greater than 48 km/h and the PCM will also freeze shift adapts from being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 81 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED TCC SOLENOID
TIME FROM START THROTTLE ANGLE
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES COMMANDED GEAR
COOLANT TEMPERATURE
DTC 82 (1-2 Shift Solenoid Circuit Electrical) will set if:
• The PCM commands the solenoid ON and the voltage input remains high (B+).
• The PCM commands the solenoid OFF and the voltage input remains low (0volts)
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Values
When this DTC sets, the PCM will command 3rd gear only, command maximum line pressure, inhibit TCC
engagement and will freeze shift adapts from being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 82 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED 2-3 SHIFT SOLENOID
TIME FROM START THROTTLE ANGLE
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES COMMANDED GEAR
COOLANT TEMPERATURE
Figure 6C2-1-48 – Transmission Solenoid Circuits
3-2 CONTROL SOLENOID VALVE
IMPORTANT: The 3–2 control solenoid valve
resistance should be a m inim um of 20–24 ohms at
20°C.
The 3-2 control solenoid valve is an ON/OFF
solenoid that is used in order to improve the 3–2
downshift. The solenoid regulates the release of
the 3–4 clutch and the 2–4 band apply.
If a voltage fault is detected in the 3–2 control
solenoid circuit, diagnostic trouble code 66 will set.
Figure 6c2-1-49 – 3-2 Control Solenoid
Legend
A Pressure Supply (AFL) 4. Filter Screen
B Exhaust 5 Plunger
C Pressure Control (3-2 Signal 6 Coil Assembly
1 Housing 7 Connector Terminal
2 Metering Ball 8 Spring
3 O-Ring
DTC 66 (3-2 Control Solenoid Circuit Electrical) will set if:
• The PCM commands the solenoid ON and the voltage input remains high (B+).
• The PCM commands the solenoid OFF and the voltage input remains low (0 volts).
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Values
When this DTC sets, the PCM will command a soft landing to 3rd gear, inhibit TCC engagement, command
maximum line pressure, inhibit 4th gear if the transmission is in hot mode and freeze shift adapts from being
updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 66 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED TFT
TIME FROM START THROTTLE ANGLE
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES COMMANDED GEAR
COOLANT TEMPERATURE
Figure 6C2-1-50 – Transmission Solenoid Circuits
TRANSMISSION PRESSURE CONTROL SOLENOID
IMPORTANT: Transmission pressure control
solenoid resistance should measure 3-5 ohms when
measured at 20°C.
The transmission pressure control solenoid is an
electronic pressure regulator that controls pressure
based on the current flow through its coil winding.
The magnetic field produced by the coil moves the
solenoid's internal valve, which varies pressure to
the pressure regulator valve.
The PCM controls the pressure control solenoid by
commanding current between 100 and 1100
milliamps. This changes the duty cycle of the
solenoid, which can range between 5 percent and
95 percent (typically less than 60 percent). 1100
milliamps corresponds to minimum line pressure,
and 100 milliamps corresponds to maximum line
pressure (if the solenoid loses power, the
transmission defaults to maximum line pressure).
The PCM commands the line pressure values,
using inputs such as the throttle position sensor.
The pressure control solenoid takes the place of
the throttle valve or the vacuum m odulator that was
used on the past model transmissions.
If the duty cycle drops below 5 percent or rises
above 95 percent, DTC 73 will set.
Figure 6C2-1-51 – Pressure Control Solenoid Valve
Legend
A Actuator Feed Limit Fluid 6. Filter Screens
B Torque Signal Fluid 7. Spool Valve
C Exhaust 8. Spool Valve Sleeve
1. Frame 9. Damper Spring
2. Spring 10. Restrictor
3. Armature 11. Push Rod
4. Variable Bleed Orifice 12. Coil Assembly
5. Spool Valve Spring
DTC 73 (PC Solenoid Circuit Electrical) will set if:
• No DTC 75 is set.
• The system voltage is between 10 and 16 volts.
• The engine is running.
• The PC solenoid valve duty cyc le reaches its high lim it (appr oximately 95%) or low lim it (approxim ately 0%) for
200 milliseconds.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
When this DTC sets, the PCM will command the PC solenoid valve OFF and freeze shift adapts from being
updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 73 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED COMMANDED PCS
TIME FROM START ACTUAL PCS
TIMES OCCURRED THROTTLE ANGLE
IGNITION CYCLES VEHICLE SPEED
COOLANT TEMPERATURE COMMANDED GEAR
Figure 6C2-1-52 Transmission Solenoid Circuits
TORQUE CONVERTER CLUTCH SOLENOID VALVE
IMPORTANT: T he T CC s olenoid r esis tanc e should
be 21 – 26 ohms minimum when measured at
20° C.
There are two DTC’s associated with the TCC
solenoid. T he f irs t DT C is 67, TCC enable solenoid.
DTC 67 is designed to detect a fault in the TCC
enable solenoid electrical circuit. While DTC 67 is
set, the PCM will inhibit 4th gear if the trans mis sion
is in hot m ode, and no TCC operation. T he second
DTC associated with the TCC enable solenoid is
DTC 69, TCC stuck on. DTC 69 is designed to
detect a TCC enable solenoid that does not
disengage. It does this by monitoring engine RPM
when the TCC is commanded off. If the engine
speed does not rise when the TCC solenoid is
disengaged the DTC 69 will set. While DTC 69 is
set, the T CC will be on in all gears or 2nd, 3rd, and
4th depending upon the failure, and the
transmission will have an early shift pattern.
The torque converter clutch solenoid valve is a
normally open exhaust valve that is used to control
torque converter clutch apply and release. When
grounded (energised) by the PCM, the TCC
solenoid valve stops converter signal oil from
exhausting. This causes converter signal oil
pressure to increase and shifts the TCC solenoid
valve into the apply position.
Legend
A Converter Feed Fluid
B Exhaust
Figure 6C2-1-53 – Torque Converter Clutch Solenoid Valve
TORQUE CONVERTER CLUTCH PWM SOLENOID VALVE
IMPORTANT: TCC PWM solenoid valve
resistance should be 10 – 11 ohms when
measured at 20°C, and 13 –15 ohms when
measured at 100°C.
The torque converter clutch PWM solenoid valve
controls the fluid acting on the converter clutch
valve, which then controls the TCC apply and
release. This solenoid is attached to the control
valve body assembly within the transmission.
The TCC PWM solenoid valve provides smooth
engagement of the torque converter clutch by
operating on a negative duty cycle with a variable
percentage of ON time.
If a fault is detected in the TCC PW M circuit, DTC
83 will set.
Legend:
A Actuator Feed Limit Fluid
B Exhaust
C Converter Clutch Signal Fluid
1. Frame
2. Armature
3. Exhaust Seat
4. Internal O-Ring
5. O-Rings
6. Metering Ball
7. Inlet Seat
8. Coil Assembly
9. Connector Terminal
Figure 6C2-1-54 – TCC PWM Solenoid Valve
DTC 67 (TCC Enable Solenoid Circuit Electrical) will set if:
• The engine is running.
• Battery voltage is between 10 and 16 volts.
• The PCM commands the solenoid ON and the voltage input remains high (B+).
• The PCM commands the solenoid OFF and the voltage input remains low (0volts).
• Conditions are met for 5 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Values
W hen this DTC sets, the PCM will inhibit TCC engagem ent, inhibit 4th gear if the transm ission is in hot mode and
freeze shift adapts from being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 69 (TCC System Stuck ON) will set if:
• No TP DTC’s set.
• No VSS DTC’s set.
• No TFP Manual Valve Position Switch DTC 28 is set.
• No TCC Solenoid Valve DTC 67 is set.
• No TCC PWM Solenoid Valve DTC 83 is set.
• The TP angle is greater than 25%.
• The engine RPM is greater than 450 for 8 seconds.
• The commanded gear is not 1st.
• The gear range is D4 or D3.
• The PCM commands TCC OFF.
• The Trans slip speed is –20 to +20 RPM.
• All conditions are met for 4 seconds.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
When this DTC sets, the PCM will freeze shift adapts from being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 83 (TCC PWM Solenoid Circuit ) will set if:
• The system voltage is 8-18 volts.
• The engine speed is greater than 300 RPM for 5 seconds.
• The engine is not in fuel cutoff.
• The PCM commands first gear.
• The TCC duty cycle is less than 10% or greater than 90%.
• The PCM commands the solenoid ON and the voltage input remains high (B+).
• The PCM commands the solenoid OFF and the voltage input remains low (0volts).
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
W hen this DTC sets, the PCM will inhibit TCC engagem ent, inhibit 4th gear if the transm ission is in hot mode and
freeze shift adapts from being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 67 , 69 AND 83 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED TCC SOLENOID
TIME FROM START THROTTLE ANGLE
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES COMMANDED GEAR
COOLANT TEMPERATURE
Figure 6C2-1-55 Transmission Solenoid Circuits
TRANSMISSION FLUID PRESSURE (TFP) MANUAL VALVE POSITION SWITCH
IMPORTANT: Seven valid combinations and two invalid combinations are available from the TFP manual valve
position switch. Refer to the TFP Manual Valve Position Switch Logic table below for valid/invalid combinations for
range signal circuits A, B and C.
Gear
Position Range
Signal A Range
Signal B Range
Signal C
Park Open 12 V Closed 0 V Open 12 V
Reverse Closed 0 V Closed 0 V Open 12 V
Neutral Open 12 V Closed 0 V Open 12 V
D Open 12 V Closed 0 V Closed 0 V
3 Open 12 V Open 12 V Closed 0 V
2 Open 12 V Open 12 V Open 12 V
1 Closed 0 V Open 12 V Open 12 V
Invalid Closed 0 V Open 12 V Closed 0 V
Invalid Closed 0 V Closed 0 V Closed 0 V
The transmission fluid pressure (TFP) manual valve
position switch (1) is a se t of f ive press ure switches (‘2’
to ‘6’) on the control valve body that sense whether
fluid pressure is present in five different valve body
passages. The combination of which switches are
open and closed is used by the PCM in order to
determine actual manual valve position. The TFP
manual valve position switch, however, cannot
distinguish between PARK and NEUTRAL because the
monitored valve body pressures are identical in both
cases.
The switches are wired to provide three signal lines
that are m onitored by the PCM. T hese inputs are us ed
to help control line pressure, torque converter clutch
apply and shift solenoid valve operation. Voltage at
each of the signal lines is either zero or twelve volts.
In order to monitor the TFP manual valve position
switch operation, the PCM compares the actual
voltage combination of the switches to a TFP
combination table stored in its memory. If the PCM
sees one of two illegal voltage combinations, a DTC 28
will result. A DTC 28 indicates a short circuit condition
in either the range signal A or the range signal C
circuits.
The TFP manual valve position switch signal voltage
can be measured from each pin-to-ground and
compared to the combination table.
Figure 6C2-1-56
On the elec trical f ive pin connec tor (7), pin N is range s ignal A, pin R is range signal B, and pin P is range signal C.
With the A/T wiring harness assembly connected and the engine running, a voltage measurement of these three
lines will indicate a high reading (near 12 volts) when a circuit is open, and a low reading (zero volts) when the
circuit is switched to ground.
The Transmission Fluid Temperature (TFT) sensor (8) is part of the TFP manual valve position switch assembly (1).
DTC 28 (TFP Valve Position Switch Circuit ) will set if:
Condition 1:
• The PCM detects an illegal TFP manual valve position switch state for 60 seconds.
Condition 2:
• The engine speed is less than 80 RPM for 0.1 second; then the engine speed is 80 – 550 RPM for 0.07
seconds; then the engine speed is greater than 500 RPM.
• The vehicle speed is less than 3 km/h.
• The PCM detects a gear range of D2, D4, or Reverse during an engine start.
• All conditions are met for 5 seconds.
Condition 3:
• The TP angle is 8 – 45%.
• The PCM commands 4th gear.
• The TCC is locked ON.
• The speed ratio is 0.65 – 0.8 (speed ratio is engine speed divided by transmission output speed).
• The PCM detects a gear range of Park or Neutral when operating in D4.
• All conditions are met for 10 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Values
W hen this DTC sets, the PCM will comm and D2 line pressure, set a D4 shift pattern and freeze shift adapts from
being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 28 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED PRNDL SWITCH
TIME FROM START TFT
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES COMMANDED GEAR
COOLANT TEMPERATURE
Figure 6C2-1 57 – TFP Switch Assembly
VEHICLE SPEED SENSOR
IMPORTANT: The sensor resistance is model dependent.
The vehicle speed sensor (1) (or transmission output speed sensor) signal is used by the PCM to control shift points
and calculate the TCC slip. The speed sensor contains a coil and a permanent magnet (3). A toothed rotor (4)
rotates past the sensor, breaking the magnetic field.
Each break in the field sends a puls e to the VSSB (Vehicle Speed Sensor Buff er). The VSSB s ends two signals to
the PCM. The first is a 2002 pulse per mile (PPM) signal that is used by the engine. The second is the transmission,
40 pulse per revolution (PPR) signal that is used in order to control the transmission.
The vehicle speed sensor (1) is located on the transmission extension housing.
The vehicle speed sensor contains a coil that has a continuous magnetic field, generated by the magnetic pick-up
(3). A voltage signal is induced in the vehicle speed sens or by teeth on the tr ansmis sion output shaft ( 4) that rotate
past the sensor and break the magnetic field. Each break in the field sends an electrical pulse from the electrical
connector (2) and wiring harness, to the PCM. The O-ring (5), prevents transmission fluid from leaking externally.
DTC 24 will set if a fault exists in the vehicle speed sensor circuit.
Figure 6C2-1-58 – Vehicle Speed Sensor
DTC 24 (Vehicle Speed Sensor Circuit Low Voltage) will set if:
• The automatic transmission is not in Park or Neutral.
• The engine speed is greater than 3,000 RPM.
• The TP Sensor angle is between 10% and 99%.
• The VSS indicates an output shaft speed of less than 3 km/h for 3 seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
For the automatic transmission, when this DTC sets, the PCM will command first gear only, command maximum
line pressure, freeze shift adapts from being updated and inhibit TCC engagement.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 24 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED THROTTLE ANGLE
TIME FROM START TFT
TIMES OCCURRED MASS AIR FLOW
IGNITION CYCLES COMMANDED GEAR (AUTO)
COOLANT TEMPERATURE VEHICLE SPEED
Figure 6C2-1-59 – VSS Circuit
AUTOMATIC TRANSMISSION FLUID TEMPERATURE SENSOR
The automatic transmission fluid temperature
(TFT) sensor (1) is part of the automatic
transmission fluid pressure (TFP) manual valve
position switch assembly (2). This sensor helps
control torque converter clutch apply and shift
quality. The T FT s ensor is a resistor , or thermis tor,
which changes value based on tem perature. At low
temperatures the resistance is high, and at high
temperatures the resistance is low.
The PCM sends a 5 volt signal to the TFT
sensor and the PCM measures the voltage
drop in the circuit. You will measure a high
voltage when the transmission is cold and
a low voltage when the transmission is hot.
Refer to the Temperature Vs Resistance table in
Section 6C2-4 SPECIFICATIONS.
If the TFT sensor circuit has a fault, DTC 58 or 59
is set. A DTC 58 indicates a short circuit condition,
while a DTC 59 indicates an open circuit condition.
DTC 79 is set if the transmission is operating at a
high temperature for a period of time.
Figure 6C2-1 -60
DTC 58 (TFT Sensor Circuit Low) will set if:
• The TFT sensor indicates a signal voltage less than 0.2 volts for 10 seconds.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Value
When this DT C s ets , the PCM uses a tr ans miss ion fluid temperatur e def ault value bas ed on engine c oolant, engine
run time and IAT at start-up. The PCM will freeze shift adapts from being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 59 (TFT Sensor Circuit High) will set if:
• The TFT sensor indicates a signal voltage greater than 4.92 volts for 6.8 minutes (409 seconds).
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Value
When this DT C s ets , the PCM uses a tr ans miss ion fluid temperatur e def ault value bas ed on engine c oolant, engine
run time and IAT at start-up. The PCM will freeze shift adapts from being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 58 AND 59 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED TFT
TIME FROM START THROTTLE ANGLE
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES COMMANDED GEAR
COOLANT TEMPERATURE
DTC 79 (Transmission Fluid Over-Temperature) will set if:
• The TFT is greater than 130° C for 10 minutes (600 seconds).
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Value
When this DTC sets, the PCM will freeze shift adapts from being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 79 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED TFT SENSOR
TIME FROM START TFT
TIMES OCCURRED THROTTLE ANGLE
IGNITION CYCLES COMMANDED GEAR
COOLANT TEMPERATURE
Figure 6C2-1-61 – TFT Sensor
DTC 85 (Transmission Slipping) will set if:
• No Throttle Position DTCs 21 or 22.
• No VSS assembly DTCs 24 or 72.
• No TCC solenoid valve DTC 67.
• No 1-2 Shift Solenoid Valve (‘A’) DTC 82.
• No 2-3 Shift Solenoid Valve (‘B’) DTC 81.
• No 3-2 Control Solenoid DTC 66.
• No TCC PWM solenoid valve DTC 83.
• The engine speed is greater than 300 RPM for 5 seconds.
• The engine is not in fuel cutoff.
• The vehicle speed is 56-105 km/h.
• The speed ratio is 0.67 – 0.90 (the speed ratio is the engine speed divided by the transmission output speed).
• The engine speed is 1,200 – 3,500 RPM.
• The engine torque is 54 – 542 Nm.
• The gear range is D4.
• The commanded gear is not 1st gear.
• The Throttle Position angle is 10 – 50%.
• The TFT is between 20 – 130°C.
• DTC 85 sets if the following conditions occur for three TCC cycles:
- The TCC is commanded ON for 5 seconds.
- The TCC is at maximum duty cycle for 1 second.
- The TCC slip speed is 80-800 RPM for 7 seconds.
IMPORTANT: The following actions may occur before the DTC sets:
• If the TCC is commanded ON and at maximum duty cycles for 5 seconds, the TP angle is 10 – 40%, and the
transm ission slip c ounter has increm ented to either 1 or 2 ( out of 3, to increm ent the fail counter for the current
ignition cycle), then the following slip conditions and actions may increment the fail counter for the current
ignition cycle:
Condition 1: If the TCC slip s peed is 80 – 800 RPM f or 7 sec onds, then the PCM will com m and m ax imum line
pressure and freeze shift adapts from being updated.
Condition 2: If condition 1 is met and the TCC slip speed is 80 – 800 RPM for 7 seconds, then the PCM will
command the TCC OFF for 1.5 seconds.
Condition 3: If c ondition 2 is m et and the T CC s lip s peed is 80 – 800 RPM f or 7 sec onds, then the fail c ounter
on the current ignition cycle is incremented.
The above s lip conditions and ac tions may be disregarded if the TCC is c ommanded OF F at any tim e, as a result of
a driving manoeuvre (sudden acceleration or deceleration).
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Value
When this DTC s ets, the PCM inhibits T CC engagem ent, com m ands m axim um line pres sure, inhibits 4th gear if the
transmission is in hot mode and will freeze shift adapts from being updated.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 85 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED TRANSMISSION SLIP SPEED
TIME FROM START TFT
TIMES OCCURRED THROTTLE ANGLE
IGNITION CYCLES VEHICLE SPEED
COOLANT TEMPERATURE COMMANDED GEAR
TRANSMISSION PASS-THRU CONNECTOR
The transmission electrical connector is an important
part of the transmission operating system. Any
interference with the electrical connection can cause
the transmission to set Diagnostic Trouble Codes
(DTC’s) or affect proper operation.
The following items can affect the electrical
connection:
• Bent pins in the connector from rough handling
during connection and disconnection.
• Wires backing away from the pins or becoming
uncrimped (in either the internal or the external
wiring harness).
• Dirt contamination entering the connector when
disconnected.
• Pins in the inter nal wiring connector back ing out of
the connector or pushed out of the connector
during reconnection.
• Excessive transmission fluid leaking into the
connector, wicking up into the external wiring
harness and degrading the wire insulation.
• Moisture intrusion in the connector.
• Low pin retention in the external connector from
excessive connection and disconnection of the
wiring connector assembly .
• Pin corrosion from contamination.
Figure 6C2-1-62
• Damaged connector assembly.
Remember the Following Points:
• In order to rem ove the connector, s queeze the two tabs toward each other ( bold arrows) and pull straight up
without pulling on the wires.
• Limit twisting or wiggling the connector during removal. Bent pins can occur.
• Do not pry the connector off with a screwdriver or other tool.
• Visually inspect the seals to ensure that they are not damaged during handling.
• In order to reinstall the external wiring connector, first align the pins by lining up the arrows on each half of the
connector. Push the connector straight down into the transmission without twisting or angling the mating
parts.
• The connector should click into place with a positive feel and/or noise.
IMPORTANT: Whenever the transmission external wiring connector is disconnected from the internal harness
and the engine is operating, DTC’s will set. Clear these DTC’s after reconnecting the external connector.
1.4 FUEL CONTROL SYSTEM
PURPOSE
The purpose of closed loop fuel control is to control tailpipe emissions consisting of hydrocarbons (HC), Carbon
Monoxide (CO), and Oxides of Nitrogen (NOx). At the same time, the system must achieve good engine
performance and good fuel economy.
The closed loop system regulates exhaust emissions by controlling the air/fuel ratio at an optimum level during
various driving c onditions. The most ef f icient air /f uel r atio to minimise ex haust emis s ions is 14.7 to 1, this allows the
3-way catalytic converter to operate at maximum efficiency to control exhaust pollutants. Because of the constant
measuring of the exhaust gases by the oxygen sensors, and adjusting of the fuel injector pulse width by the PCM,
the fuel injection system is called a "closed-loop" control system.
FUNCTION
The f uel s upply sys tem delivers f uel at a r egulated pres s ur e to the f uel ra il. T he f uel inj ec tor s, located direc tly ahead
of each inlet port of the cylinder head, act as fuel flow control valves, "spraying" atomised fuel into the inlet ports
when they are electric ally "pulsed" by the PCM. O n this engine, all inj ec tors ar e wired individually so they are puls ed
individually. This type of fuel injection is referred to as sequential injection because pulsation of the injectors are
individually controlled and in a specific order.
The PCM controls the am ount of fuel injec ted into the engine by contr olling the length of tim e the injectors are held
open. This "length-of-time" is called PULSE WIDTH. To increase the amount of fuel injected, the pulse width is
lengthened, and vice versa. T he pulse width is calibratable and varies between 0 – 11 millis econds with the engine
running at idle, and injection pulses normally occur once every two crankshaft revolutions.
MASS AIR FLOW SYSTEM
The Holden/Delco Fuel Injection system is a Mass Air Flow system. The system is based upon an Air Meter that
measures the mass air flow rate of the engine directly.
Advantages of Mass Air Flow:
• Base engine components can be changed.
• Automatically compensates for engine ageing.
• No air measurement lag time.
• Excellent idle stability.
Two specific data sensors provide the PCM with the basic information for the fuel management portion of its
operation. That is , two specific signals; crank shaf t referenc e signal from the ignition system, and the Mass Air Flow
(MAF) s ensor signal. Both of these s ignals to the PCM establish the engine speed and m ass of air ingested by the
engine. Due to the additional temper ature compens ation sensor in the MAF sens or, this sys tem does not requir e a
manifold absolute pressure sensor.
The engine speed signal comes from the ignition module to the PCM on the crankshaft reference signal input
circuit. The PCM uses RPM inform ation to calculate the best fuel injector pulse width and spark timing for a given
operating RPM band.
The mass of air ingested by the engine is sent as a signal from the mass air flow sensor to the PCM.
When the engine is started, the PCM will im m ediately look at the Engine Coolant Temper ature sens or to determ ine
how much fuel is required to start the engine. After the engine is started, the PCM will constantly monitor the MAF
sensor values to determine both the spark advance and engine fuelling requirements. The Mass Air Flow sensor
measures the mass of air ingested into the engine.
The PCM then c alc ulates how much fuel to be injec ted to maintain an air /f uel ratio of 14.7 to 1. An engine star ted in
cold weather will require m ore f uel and spark advance than an engine s tarted hot, which r equires les s fuel and les s
spark advance.
One sensor is used to m eas ure the density factor, the Mas s Air F low (MAF) sens or. T he m ass air flow sensor used
on this engine utilises a heated element type of operation. Three sensing elements are used in this system.
As air passes over the heated elements during engine operation they begin to cool. By measuring the amount of
electrical current required to maintain the heated elements at the predetermined temperature above ambient
temperature mass air flow rate can be determined.
The s ignal that is s ent f r om the mass air flow sensor is s ent in the f orm of a frequenc y output. A large quantity of air
passing through the sensor (such as when accelerating) will be indicated as a high frequency output. A small
quantity of air passing through the sensor will be indicated as a low frequency output (such as deceleration or at
idle). The Tech 2 scan tool displays MAF sensor information in frequency and grams per second. A "normal"
reading is approximately 4 - 9 grams per second at idle and increases with engine RPM.
As the PCM r eceives this f requency signal from the mas s air flow sens or, it searches its pre-progr amm ed tables of
information to determine the pulse width of the fuel injectors required to match the mass air flow signals.
The remaining sensors and switches provide electrical inputs to the PCM which are used for modification of the
air/fuel mixture as well as for other PCM control functions, such as Idle Air Control (IAC).
MODES OF OPERATION
The PCM looks at voltage s ignals f r om s everal s ens ors to deter mine how much fuel to give the engine, and when to
operate in the open-loop or c losed-loop m odes. The f uel delivery is controlled in one of s everal possible m odes. All
the modes are controlled by the PCM, and are described in the following paragraphs.
Starting Mode
When the ignition key is first tur ned "ON," the PCM will energis e the f uel pump r elay, and the fuel pum p will build up
pressure to the fuel rail. The PCM then checks the engine coolant temperature sensor and determines the proper
injector pulse width for starting the engine.
When crank ing begins , the PCM will operate in the Starting Mode until engine RPM is more than about 400, - or- the
"Clear Flood" m ode is enabled. After the ignition is turned "ON" and the first reference signal is received, the PCM
will pulse all of the fuel injectors. After the first prime pulse has been injected, the PCM will wait until a good
cam shaf t position s ignal is rece ived. When the PCM receives a good c am shaf t position signal, the fuel injec tors will
be activated in Sequential Mode. Pulse width during the Starting Mode is between approximately 4 – 26
milliseconds, depending upon engine coolant temperature.
Clear Flood Mode
If the engine floods, it can be started by pushing the accelerator pedal down all the way to the floor while crank ing
the engine. The PCM then s tops pulsing the injec tors (zero m illisecond pulse width), which should "c lear" a flooded
engine. The PCM holds this pulse width as long as the throttle position sensor input indicates the throttle is above
80% and RPM is below 400.
If the throttle is held wide-open while attempting to make a normal start with a non-flooded engine, the
engine will not start.
Normal Open Loop Mode
After the engine is running (RPM more than 400), the PCM will operate the fuel control system in the Open Loop
mode. In open loop, the PCM ignores the signal from the Oxygen Sensors (O2S), and calculates the air/fuel ratio
injector pulse width based on inputs from the crankshaft reference signal (RPM input) and these sensors: MAF, IAT,
ECT, and TP sensor.
The system will stay in the Open Loop mode until all the Closed Loop m ode criteria have been met, or not at idle,
refer Open Loop Idle Mode description.
In open loop, the calculated puls e width may give an air/fuel ratio other than 14.7 to 1. An exam ple of this would be
when the engine is cold, because a richer mixture is needed to ensure good driveability.
The normal open loop mode is not active when adverse or abnormal vehicle operating conditions are occurring.
Adverse conditions include engine overheating due to high vehicle speed or high ambient temperature.
Open Loop Idle Mode
The reas on for the Idle Mode is to allow a slightly richer mix ture at idle for better idle quality. Idle Mode air/fuel ratio
is about 14.0 to 1. This is an open loop mode, meaning the O2 sensor signals are ignored.
The Open Loop Idle Mode is in effect when the throttle is closed (TP Sensor), and vehicle speed is below 5 km/h
(VSS).
In the c ase where the vehicle r olls to a st op while operating in the Closed Loop m ode, Idle Mode will be delayed f or
about 20-30 seconds. During this time, the PCM will "learn" a fuel correction factor for a 14.7 to 1 air/fuel ratio
before switching to the Idle Mode.
Closed Loop Mode
In Closed Loop mode, the PCM initially calculates injector pulse width based on the same sensors used in open
loop. T he diff erence is that in closed loop, the PCM us es the Exhaust G as Oxygen Sensor (O2S) signals to m odify
and precisely fine tune the fuel puls e width calculations in order to pr ecisely maintain the 14.7 to 1 air/f uel ratio that
allows the catalytic converter to operate at it's maximum conversion efficiency.
Delta TPS Acceleration Mode
The PCM look s at rapid changes in throttle position (TP sensor) to increase engine power, and provides extra fuel
by inc reasing the injector pulse width. If the increas ed fuel requirem ents are gr eat enough, the PCM may add ex tra
fuel injection pulses between the injector pulses that normally occur once per engine cycle.
Lean Cruise Air/Fuel Mode
During steady state cruising, the air/fuel ratio is made lower in order to increase fuel economy.
The engine will operate in Lean Cruise when:
• ECT is greater than 80° C.
• VSS is greater than 70 km/h.
• Engine has been running longer than 2 minutes and 30 seconds.
• Calculated A/F ratio is 14.8 to 1
• Engine is not in power enrichment mode.
If all the criteria are met, the PCM will lean out the A/F ratio by 0.1 ratio every 0.2 second until it reaches its
maximum total enleanment.
Deceleration Mode
W hen deceleration occurs, the fuel remaining in the intake manifold can cause excessive emissions and possibly
backfiring. Again, the PCM looks at changes in throttle position (TP sensor) and engine RPM and reduces the
amount of fuel by decreasing the pulse width, but does not completely shut off the fuel.
Decel Fuel Cutoff Mode
Decel fuel cutoff disables fuel delivery during a deceleration to reduce emissions and to improve fuel economy.
When deceleration fr om road s peed oc cur s , the PCM can c ut of f fuel pulses completely f or short periods. T he decel
fuel cutoff mode occurs when all these conditions are met:
1. Coolant temperature above 63° C.
2. Engine RPM has dropped more than 200 RPM.
3. Vehicle speed above 42 km/h.
4. Throttle is less than 2 %.
When the decel fuel cutoff is in effect, any one of these can cause the injection pulses to restart.
1. Engine RPM has not dropped more than 200 RPM.
2. Vehicle speed is less than 42 km/h.
3. Throttle is open at least 2%.
Park/Neutral To Drive Acceleration Enrichment Mode
The PCM will deliver additional fuel to the engine to reduce the RPM droop associated with a transmission shift from
park/neutral to a drive shift. This mode will only add fuel based on the first 32 reference pulses after a shift has been
detected.
Power Enrichment (PE) Mode
The Power Enrichment (PE) mode delivers a rich mixture to the cylinders during a large throttle position change
com mand fr om the driver. Dur ing ‘PE’, the PCM will not m ake f uelling changes based on the oxygen sensor signal
(this is an open loop mode of operation).
Battery Voltage Correction Mode
At low battery voltages, the ignition system m ay deliver a weak spar k, and the injector m echanical movement tak es
longer to "open." The PCM will compensate by:
• Increasing ignition coil dwell time if voltage is less than 12 volts.
• Increasing idle RPM if voltage drops below 10 volts.
• Increasing injector pulse width if voltage drops below 10 volts.
Fuel Cutoff Mode
No fuel is delivered by the injectors when the ignition is (OFF). This prevents dieselling. Also, fuel pulses are not
delivered if the PCM receives no crankshaft reference pulses from the ignition module, which m eans the engine is
not running.
The Fuel Cutoff Mode is also enabled at:
• High engine RPM, as an over-speed protection for the engine. When cutoff is in effect due to high RPM,
injection pulses will resume after engine RPM drops slightly.
• High vehicle speed. When the vehicle speed exc eeds a calibr atable value the fuel base pulse width is set equal
to zero. Normal fuel operation will return when the vehicle speed falls below a calibratable value.
Sequential Fuel Injection Mode
When the engine is first cranked over, all injectors will be energised simultaneously. After the engine has been
started and a good camshaft signal has been processed, the PCM will energise each individual injector in the
normal firing order. This mode of operation helps to stabilise idle, reduce emissions and reduce fluctuations in fuel
pressure.
CAMSHA FT POSITION SENSOR
The Cams haf t Position Sens or (1) (C MP) is loc ated
in the engine front cover, behind and below the
water pump, near the camshaft sprocket.
As the cam shaf t spr ock et turns, a m agnet mounted
on it activates the Hall Ef f ec t s witch in the c amshaft
position sensor. When the Hall Effect switch is
activated, it ground's the signal line to the DIS
module, pulling the camshaft position signal line's
applied voltage low. This is interpreted as a
camshaft position signal (Synchronisation Pulse).
Because of the way the signal is created by the
camshaft position sensor, the signal circuit is
always either at a high or low voltage.
While the camshaft sprocket continues to turn, the
Hall Eff ect switch turns "OFF" as the m agnetic f ield
passes the camshaft position sensor, resulting in
one signal each time the camshaft makes one
revolution.
1
4205
Figure 6C2-1-63 Camshaft Position Sensor
The c amshaf t position signal, which actually repr esents cam shaft position due to the sensor's mounting location, is
used by the PCM to properly time its sequential fuel injection operation.
Refer to Figs. 6C2-1-11 and 6C2-1-12 in this Section for camshaft position sensor location and camshaft position
signal details.
When the camshaft position signal is not received by the PCM, a DTC 48 will be set. An intermittent camshaft
position signal will set a DTC 49. If either of these DTCs are set, the fuel system will not be in sequential fuel
injection mode.
Adaptive Learning
Adaptive learning is the ability of the on-board computer to determine and remember its most recent operating
experience. The PCM uses this remem bered infor mation to "learn f rom experienc e" and to mak e adjustments with
respect to what it learnt. If the engine were to develop a restricted fuel filter, the PCM will change the fuel injector
pulse width richer to compens ate f or this condition and will remember to keep this fuel injector pulse in memory until
the restriction is corrected. After the restriction has been fixed, the PCM will eventually go back to the original pre-
programmed fuel injector pulse.
Adaptive learning is an on-going process that continues throughout the life of the engine. A new engine with good
com pres sion will have good vacuum . As the engine wears and c om press ion decreas es, a slight dec rease in engine
vacuum will be noticed, which translates into a slightly lower MAF grams per second at idle, which will decrease
injector pulse width to compensate for this condition.
SHORT TERM FUEL TRIM
Short T erm Fuel Trim (STFT ) represents short term corrections to the f uel injector pulse width calculations, based
on the oxygen sensor input signals to the PCM.
When the engine is started cold, in "Open Loop," the PCM will control the fuel injection pulse width based upon
various sensor inputs such as RPM, ECT, MAF and TP sensor until the oxygen sensors become hot enough
(approxim ately 360° C) to operate properly. During this "Open Loop" period, both Shor t Ter m Fuel T rim (STF T) and
Long Term Fuel Trim (LTFT) are disabled and will read 0% on a Tech 2 scan tool.
W hen the oxygen sensor s have reac hed their norm al operating temper ature (approxim ately 600° C or above), they
will produce a varying voltage to the PCM and provide a good indication of what has happened in the combustion
chambers.
At this time the PCM will switch from "Open Loop" to "Closed Loop" and the STFT will start to constantly monitor the
oxygen sensor signals, so that the PCM can modify fuel injector pulse width with greater accuracy than in "Open
Loop".
STFT monitors the oxygen sensor signals so that it can adjust the fuel injector pulse width to maintain an air/fuel
ratio of 14.7 to 1 f or max imum catalytic converter ef ficiency. An STFT value of 0% is equivalent to an air/fuel ratio of
14.7 to 1 and an average oxygen sensor signal voltage of 450 mV.
The normal pos ition f or Shor t T er m Fuel Trim is 0%, any change from this value indica tes the Shor t Term Fuel T rim
is c hanging the f uel injec tor pulse width. The am ount of pulse width change depends upon how far the STF T value
is f r om 0%. If the STFT value is above 0%, the f uel inj ec tor pulse width is being inc reas ed, thus adding more fuel. If
the STFT value is below 0%, the fuel injector pulse width is being decreased, thus removing fuel. The normal
operating range of STFT is considered to be between -22% and +25% ; any value out of this range is usually
caused by a malfunction.
If an engine has a r es tr icted fuel filter, the low fuel pr es sur e will res ult in les s fuel being injec ted and allows mor e air
into the air c harge than is needed to ignite the am ount of f uel the f uel injector has injec ted, theref ore, a lean air/f uel
ratio exists in the combustion chamber. After combustion has taken place, the exhaust gases still contain more
oxygen content than nor mal and the oxygen sensor r eads this as low voltage, say 200 mV. T he STFT detec ts that
the oxygen sensor s ignal is low and will inc reas e the value to r ichen up the air /f uel mixt ure. O n a Tech 2 s c an tool it
will display STFT as a value above 0%. This STFT change will increase the injector pulse width allowing the fuel
injectors to stay open longer and inject more fuel.
If the additional fuel was injected and the oxygen sensor signal voltage is still low, the STFT will continue to increase
its value until the oxygen sensor signal voltage goes above 450 mV. If the STFT continues to detect a low oxygen
sensor signal voltage it will continue to try and compensate for the lean exhaust condition until it runs out of its
authority in the partic ular Long T e rm F uel T r im (L T F T ) c ell it's oper ating in. At this point, the PCM will res et STFT to
0% and go through this procedure again until it can control the system.
If af ter a specified am ount of resets have been tried and failed, the PCM k nows that it cannot control for the failure
and the STFT will remain at its maximum value.
STFT values are bas ed on the oxygen s ensor signal voltage reading, ther efore, ST FT is used by the PCM to mak e
quick changes to the fuel injector pulse width over a short period of time.
LONG TERM FUEL TRIM
Long Term Fuel Trim is used to adjust for engine to engine variation and to adjust for engine ageing. LTFT is a
portion of the PCM memory used to adjust fuel delivery across all operating conditions of the engine. The PCM
monitors the STFT and will adjust the long term trend of the fuel injector pulse width if the STFT has been at a value
for a certain period of time. LTFT is used to change the long term fuel injector pulse width and is only operational
when the fuel control system is in "Closed Loop." A normal LTFT value is 0% and should follow the STFT value.
If an engine has a res tricted fuel filter , the low f uel pressure will res ult in less fuel being injec ted and will cause the
STFT value to go higher than 0% to s ay, 2%. If this STF T value c hange does not com pensate for the restricted fuel
filter, the PCM will continue to increase the STFT value. The STFT may climb as high as its maximum calibrated
value if there is a severe restriction. The PCM will continue to monitor STFT as it climbs, but it will not make any
changes to the f uel injector puls e width for a specif ic period of time. Af ter a specif ic period of tim e has elapsed and
the STFT value has remained above say +8%, the LTFT will move up to say 4% and wait again to detect if the
STFT has dropped bac k down to 0%. If not, the ST F T will gradually move toward its max imum c alibr ated value limit
until it gains control of the fuel injection system. If STFT and LTFT are both set at their maximum value limit, the fuel
control system is "out of the limits of control" and will set either a Diagnostic Trouble Code (DTC) 44, or DTC 64
(lean exhaust) or DTC 45, or DTC 65 (rich exhaust) and go into "open loop" operation.
Under the conditions of power enrichm ent, ( Wide Open T hrottle, WOT ), the PCM sets the STFT to 0% and f reezes
it there until power enrichment is no longer in effect. This is done so that LTFT will not try to correct for the
commanded richness of power enrichment.
The PCM will keep the latest LTFT values stored in its LTFT memory cells. MAF sensor readings (‘H’) and engine
RPM (‘G’) are used by the LTFT to determine what cell to read. LTFT values are stored in the PCM's long term
memor y, for us e each tim e the engine's RPM and load m atches one of the LT FT cells. All LT FT values ar e reset to
0% when the PCM's "long term memory power supply" is disconnected, as when diagnostic trouble codes are
cleared. The Tech 2 scan tool also has the ability to reset LTFT to 0% with a special command.
Figure 6C2-1-64 – Long Term Fuel Trim Values
Legend
A. Throttle Position (%)
B. Air Flow (mg/Cyl)
C. Vehicle Speed (km/h)
D. Engine Speed (RPM)
E. Light Percentage Canister Purge
F. Heavy Percentage Canister
Purge
G. Engine Speed (RPM)
H. Air Flow (mg/Cyl)
J. Idle (Manual Transmission Only)
1. Hysteresis
LONG TERM FUEL TRIM CELLS
The Long Term F uel T r im f unc tion of the PCM is divided up into c ells ar r anged by Mass Air Flow (MAF) and Engine
Speed (RPM). Each cell corresponds to a region on a MAF vs RPM table. Each region is calibrated to an LTFT
value of 0%. A value of 0% in a given block indicates no fuel adj ustm ent is needed f or that engine load c ondition. A
higher number, say + 4%, indicates that the PCM has detected a lean exhaust indication under those conditions,
and is adding fuel (increasing fuel injector pulse width) to compensate. Conversely, a lower number, say -6%,
indicates that the PCM has detected a rich exhaust indication under those load conditions, and is subtracting fuel
(decreasing fuel injector pulse width) to compensate.
As the vehicle is driven from a standing start and accelerated or decelerated from various engine speeds, the
engine's LTFT calibration will change from one cell to another cell. As the LTFT changes cell so does STFT,
however, STFT will only make short term corrections in whatever LTFT cell the engine is operating in. W hen the
engine is idling, it can be in one of two cells. On a vehicle with automatic transmission, depending upon canister
purge, the engine will idle in cell 0 or 17. If the engine was running at idle and the canister purge was "ON", we
would be in cell number 0 on an automatic transmission equipped vehicle.
Cells 16 and 33 are used f or idle on vehicles with m anual transm ission only. As the Supercharged V6 engine is not
available with this transmission, these cells are not programmed for this application.
Whatever cell the engine is oper ating in, the PCM will read that cell's particular LT FT value and electr onically adjust
the fuel injector base pulse width to compensate for a rich or lean condition in the engine. If an engine has a
restric ted fuel f ilter and the custom er has dr iven the vehicle like this f or quite some time, the STF T value would be
high, and the PCM would be compensating for this condition by adding more fuel. Because the STFT value is above
0%, LTFT will also be greater than 0% in most of the cells to compensate for the lean exhaust. If you suspect a
driveability problem ass ociated with an over rich or over lean c ondition, then use the STFT value to detect what the
fuel control system is doing at the present time. Use the LTFT to identify what the system has "learned" over a
greater period of time to compensate for the condition.
Use the LTFT cells to determine if the fuel control system is commanding rich or lean throughout the operating
range. If it is only rich or lean at idle or part throttle, look for components that would cause problems in these areas.
All LT FT c ell values are rese t to 0% when long term memor y power to the PCM is rem oved, s uch as when clearing
DTC's.
The Tech 2 scan tool has the ability to reset all LTFT cells to 0% with a special command.
A system malf unction that caus es too great a diff erence between the right and left Short T erm Fuel T rim values or
too great a difference between the right and left Long Term Fuel Trim values will set either a DTC 78 or DTC 76.
Figure 6C2-1-65 Long Term Fuel Trim Cell Matrix
Legend
A. Throttle Position (%)
B. Air Flow (mg/Cyl)
C. Vehicle Speed (km/h)
D. Engine Speed (RPM)
E. Light Canister Purge
F. Heavy Canister Purge
G. Engine Speed (RPM)
H. Air Flow (mg/Cyl)
J. Idle (Manual Transmission Only)
1. Hysteresis
DTC 76 (Short Term Fuel Trim (STFT) Delta High) will set if:
• The lef t hand short term fuel trim value varies from the right hand short term fuel trim value by mor e than 63%
for more than 32 seconds
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
DTC 78 (Long Term Fuel Trim (LTFT) Delta High) will set if:
• The lef t hand long ter m f uel trim value var ies from the right hand long ter m f uel trim value by more than 59% for
more than 32 seconds.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
Once DTC 76 or 78 are set, and current, the PCM will operate the fuel system in the open loop mode.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 76 AND 78 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED L.H STFT
TIME FROM START R.H LTFT
TIMES OCCURRED L.H LTFT
IGNITION CYCLES R.H O2 SENSOR
R.H STFT L.H O2 SENSOR
BASIC FUEL SYSTEM OPERA TION
The f uel control system starts with the fuel in the f uel tank. A single in- tank high pres sure fuel pump (located inside
a modular sender unit) is used. F rom the high press ure pump, f uel f lows through a fuel filter, then on to the engine
fuel rail through the fuel pressure supply line.
The high pressure in-tank single pump is capable of providing fuel at more than 414 kPa. A pressure regulator
connects between the fuel rail and the return fuel line, and keeps fuel available to the injectors at a regulated
pressur e between 270 and 350 k Pa. The r egulated press ure will vary, depending on intake m anifold pres sure. T he
pressur e regulator s enses m anifold press ure through a sm all hose connec ting it to the throttle body adapter. W hen
throttle body adaptor pressure is low (closed-throttle), the regulated pressure is at its lowest. When the throttle is
wide open, intake manifold pressure is high and the fuel pressure also is at its highest.
Fuel in ex ces s of inj ec tor needs is r eturned to the fuel tank by the separate return line c onnected to the outlet of the
pressure regulator.
The injectors, located in each runner of the intake manifold just ahead of the inlet ports to the cylinder head, are
controlled by the PCM. They deliver fuel in one of several modes, as described previously .
The fuel pump is energised by the PCM via the fuel pump relay. Refer to A–4.1 in Section 6C2-2A DIAGNOSTIC
TABLES for diagnosis of the fuel pump electrical system.
SYSTEM COMPONENTS
The Fuel Control System is made up of the following components:
• PCM
• Fuel pressure supply line
• Fuel pump relay
• Fuel pump control module
• Fuel rail
• Fuel injectors
• Modular fuel sender assembly
• Fuel pump assembly
• Fuel pressure regulator
• Fuel filter
• Fuel return line
Prior To Starting Engine, Check Fuel System For Leaks As Follows:
1. Turn ignition “ON”.
2. Check fuel system for leaks at the points
indicated (), with the fuel pump running.
3. Repair leaks if present.
Legend:
1. Modular Fuel Sender Assembly
2. Fuel Pump Harness Assembly
3. Fuel Supply Line
4. Fuel Filter
5. Fuel Return Line
6. Vapour Line
7. Fuel Tank
Figure 6C2-1-66 – Fuel System Leak Checkpoints
Modular Fuel Sender Assembly
The modular fuel sender assembly is inserted into
the top of the f uel tank, and extends from the top to
the bottom of the fuel tank .
Legend:
A. Fuel Flow In
B. Fuel Flow Return
C. Fuel Vapour
1. Aspirator
2. Jet Pump Fil ter
3. External Strainer
4. Primary Umbrella V al ve
5. Sec ondary Umbrell a Valve
6. Internal Strainer
7. Roller V ane Fuel Pump
A ceram ic fuel level s ensor as sem bly (not shown in
Figure 6C2-1-67), consists of the following:
• A Float
• The Wire Float Arm
• A Rheostat
The fuel level is sensed by the position of the float
and float arm. The amount of current passing
through the rheostat varies with a position change,
and this modifies the fuel gauge reading on the
instrument panel.
The V6 Supercharged Engine application uses a
rollervane fuel pump. This fuel pump can only be
serviced as a complete unit with the sender unit
assembly.
Figure 6C2-1-67 Modular Sender Assembly
Figure 6C2-1-68 – V6 Supercharged Engine Rollervane Fuel Pump Assembly
Legend
1. End Cap
2. RFI Module
3. Relief Valve
4. Outlet Plate
5. Rotor
6. Rollers
7. Eccentric Ring
8. Bearing
9. Face Plate
10. Rivets
11. Housing
12. Impeller
13. Inlet Body
14. Aluminium Shell
15. Electric Motor
Throttle Body Unit
The throttle body unit (3) is made up of a single
casting, with two electrical components connected
to it.
They are:
1. An Idle Air Control (IAC) valve (1) to control air
flow bypassing around the throttle blade. This
"bypass" airflow provides the air requirements
for the engine when the throttle is clos ed. More
"bypass" air gives the engine the ability of a
higher idle speed, while lower flow rates of this
"bypass" air give lower idle speeds. The IAC
acts as a PCM-controlled bypass air valve,
allowing the PCM to control idle speed.
2. A T hrottle Pos ition Sensor (2) , which gives the
PCM inform ation about c urrent thr ottle position,
and if the throttle is moving (opening or
closing). The PCM can also determine how
quickly the throttle is opening or closing with
this signal.
The throttle body contains 2 vacuum ports. The
small port provides manifold vacuum to the
evaporative emission's canister purge solenoid.
The larger port is for the positive crankcase
ventilation system.
Figure 6C2-1-69 Throttle Body with TPS and IAC
Idle Inspection
For this engine applic ation, the engine idle mus t be
checked every 80,000km. If the Idle Air Control
(IAC) Valve steps displayed on the Tech 2 are
greater than 25 at idle, the throttle body will need to
be removed and cleaned.
For throttle body cleaning procedure, Refer to
Section 6C2-3 SERVICE OPERATIONS.
Although the throttle body for this application looks
very similar to the V6 Non-Supercharged engine
application, it is specific to this engine.
Both the small air flow hole in the throttle blade
above the throttle blade shaft and the redesigned
Idle Air Control (IAC) valve air passage, are
retained fr om the previous model that assis ts in idle
quality improvement and helps to prevent engine
stalling.
Legend:
1. Throttle Body Assembly
2. TP Sensor
3. IAC Valve
4. Throttle Blade
Figure 6C2-1-70 Throttle Body Identification
Fuel Injectors
The f uel injec tors ar e electric ally operated, fuel flow
control valves. They are supplied with +12 volts
through a Fuse and EFI relay, both located in the
engine compartment, fuse and relay housing.
The injectors are controlled by the PCM providing
the ground c irc uit. T he PCM ener gis es the inj ec tors
to "open" the flow of fuel. The injectors are never
fully energised "ON," as that would flood the engine
with too much fuel. The PCM supplies the ground
circuit in short pulses. The longer the duration of
the pulse (pulse width), the more fuel is injected
into the engine.
Inside, the injectors have a coil of electrical wire
that becomes an electromagnet when energised.
The resistance of these windings is important for
the PCM to operate correctly. The injector
electrical resistance is approximately 12.2 Ω
ΩΩ
Ω
@ 20°
°°
° C. If measurement with an accurate
ohmmeter sho ws less than 11.8 Ω
ΩΩ
Ω or more than
12.8 Ω
ΩΩ
Ω, at this temperature, replace the injector.
(An acceptable resistance range would be 11.8-
12.8 Ω).
A fuel injector that does not open, will cause a
misfire condition, while an injector that is stuck
partly open, could cause dieselling (or ‘run-on’).
This occurs because some fuel would be delivered
to the engine after the ignition key was turned
‘OFF’.
Figure 6C2-1-71 – Fuel Injector
Legend:
1. Supercharged Injector
2. Non-Supercharged Injector
If a voltage fault occurs at PCM terminal X1-B12, DTC 57 will set.
DTC 57 (Injector Voltage Monitor Fault) will set if:
• The engine is running.
• DTC 54 is not set.
• Injector voltage monitor line voltage is 2.2 volts different than system voltage for 3 seconds.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
There are no default values.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 57 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED BATTERY VOLTAGE
TIME FROM START REFERENCE VOLTS
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES INJECTOR VOLTAGE
COOLANT TEMPERATURE
Figure 6C2-1-72 Injector Circuit
Fuel Pressure Regulator
The fuel pressure regulator is a diaphragm-operated relief valve with fuel pump pressure on one side and intake
manifold pressure (engine vacuum) combined with mechanical spring pressure on the other. The function of the
regulator is to maintain a regulated pressure at the injectors at all times by controlling the flow into the return line.
The fuel pressure regulator is mounted on the fuel rail and may be serviced separately.
If the fuel pressure is too low, poor performance and a DTC 44, or 64 could set. If the pressure is too high,
excess ive odour and a DTC 45, or 65 m ay result. Ref er to Table A- 4.1 for inform ation on diagnosing f uel pressur e
conditions.
Figure 6C2-1-73
Legend
A. Fuel In
B. Fuel Out
1. Valve
2. Diaphragm
3. Fuel Pressure Regulator
4. Compression Spring
5. Vacuum Connection
6. Fuel Pressure Regulator Location
Fuel Filter
The fuel filter is located under the vehicle by the
right hand rear side frame, forward of the fuel tank.
The fuel filter is mounted in place by a plastic
retaining strap attached to the rear frame. Both
fuel pressure hoses at the filter are quick connects
to the filter. These quick connections can be
removed by squeezing the oval shaped
connections at the filter.
As there is a specific procedure for
replacement of the fuel filter, Refer to
Section 6C2-3 SERVICE OPERATIONS.
Legend:
1. Fuel Vapour – Canister To Engine
2. Atmospheric Vent
3. Fuel Vapour Purge Line
4. Fuel Feed Line
5. Fuel Tank
6. Flow Arrow
7. Fuel Filter
8. Fuel Return Line
9. EVAP Canister
Figure 6C2-1-74 Fuel Filter Location
Fuel Pump Electrical Circuits Supercharged Engine
When the ignition switch is turned to "O N" or “Cr ank” after having been "OFF" f or at leas t 10 seconds , the PCM will
immediately energise the fuel pump r elay, which will then activate the Fuel Pump Control Module to oper ate the f uel
pump. This builds up the fuel pressure quickly. If the engine is not cranked within two seconds, the PCM will shut
the fuel pump relay "OFF" and wait until the engine is cranked. As soon as the engine begins cranking, the PCM will
sense the engine turning from the crankshaft reference input, and turn the relay "ON" again to run the fuel pump.
A failed fuel pump relay circuit will cause a no start condition.
6C2-1-75 Fuel Pump Electrical Circuits V6 Supercharged Engine
The fuel pum p r elay (1) is located in the under hood
electrical centre in the engine compartment.
Figure 6C2-1-76 Fuel Pump Relay Location
Fuel Pump Control Module
The V6 Supercharged engine utilises a two speed
Fuel Pump and a Fuel Pump Control module. The
Fuel Pump Control Module is located in the boot,
as shown. T he Fuel Pum p Control Module can vary
the fuel pump output depending on the required
engine load. W hen the ignition is first turned "ON",
the PCM energises the fuel pump relay, which
applies power to the Fuel Pump Control Module.
The fuel pump will then pressurise the fuel system.
The purpose for the Fuel Pump Control Module is
that this Supercharged system requires more fuel
volume under heavy engine load conditions than
the non-superc harged system. T he fuel pum p used
in the non-superc harged system m ay be capable of
supplying the required fuel volume for the
supercharged system, but with the increased fuel
volume required, the non-supercharged fuel pump
would eventually fa il from r unning at the higher f uel
volume.
The PCM controls the current flow through the fuel
pump with a Pulse W idth Modulation (PW M) s ignal
at 128 Hertz (Hz) to the fuel pump control module.
The fuel pump control module controls the current
flow through the fuel pum p depending on the PWM
signal received from the PCM.
Figure 6C2-1-77 Fuel Pump Control Module Location
Under nor mal driving conditions the requir ed fuel volume is less, so the fuel pum p operates at a duty cycle of 67%
"ON", that is the PCM c ontrols the f uel pump c irc uit, via the f uel pump c ontrol module at 67% "O N" and 33% "O FF ",
at a frequency of 128 Hz.
W hen the engine load is increased, as measured by the Mass Air Flow sensor, the fuel pump control module will
switch fr om the norm al duty cycle (67%) to a higher duty cycle (100%) bas ed on the c om m and from the PCM. This
higher duty cycle will increase the cur rent supply through the fuel pum p, inc reasing the f uel volum e delivered by the
fuel pump.
Another feature of this Fuel Pump Control Module is that, when the fuel pump is running at the lower duty cycle
(normal driving conditions), the returned fuel to the fuel tank (from the fuel pressure regulator) is less. This lower
volume of returned fuel to the fuel tank will result in lower emissions (fuel tank vapours).
Also with the fuel pum p running at a lower duty cycle (norm al driving conditions), the voltage output required to run
the pump is lower. This will require less generator output and will decrease overall vehicle fuel usage.
Refer to Table A-4.1 for diagnosis of the fuel pump electrical circuit.
1.5 IDLE AIR CONTROL (IAC) VALVE
The purpose of the Idle Air Control (IAC) valve (5)
is to control engine idle speed, and prevent stalls
due to changes in engine load at idle.
The IAC valve, mounted in the throttle body (4),
controls bypass air ar ound the throttle valve (3). By
extending the pintle (1) (to decrease airflow) or
retracting the pintle (to increase airflow), a
controlled amount of air can move around the
throttle valve (3). If RPM is too low, more air is
bypassed around the throttle valve to increase
RPM. If RPM is too high, less air is bypassed
around the throttle valve to decrease RPM.
The IAC valve moves in small steps numbered
from 0 (extended pintle, bypass air passage fully
shut) to 255 (retracted pintle, maximum bypass
airflow) as commanded by the PCM.
At idle, the desired position of the IAC valve is
calculated by the PCM based on coolant
temperature, actual engine RPM, engine load, and
battery voltage and sent via the wring harness (6)
to the stepper motor in the IAC Valve (5).
If the IAC valve is disconnected or reconnected
with the engine running, the PCM can "lose track"
of the actual pos ition of the IAC. T his also happens
when PCM's keep alive memory voltage, i.e., PCM
connectors , Engine fus e F29, or battery cables, are
disconnected. If this happens, the PCM will "reset"
the IAC. After the engine has been run for at least 5
seconds, then upon ignition "OFF" the IAC will be
reset.
Figure 6C2-1-78 – IAC Valve
The "reset" procedure is as follows:
1. T he PCM com m ands the IAC to shut the idle air pass ageway in the throttle body. It does so, by issuing enough
"extend" pulses to move the IAC pintle fully shut in the bore, regardless of where the actual position was.
2. Then, the PCM calculates the IAC is at a fully shut position, and calls that position "0 steps." Next, the PCM
issues "retract" steps to properly position the pintle.
The IAC can also be reset with the engine running, by a special command on the Tech 2 scan tool.
The IAC valve affects only the idle RPM of the engine. If it is open fully, too much air will be allowed into the
manifold and idle speed will be too high. If it is st uck c losed, too little air will be allowed into the intake manif old, and
idle speed will be too low.
A system malfunction that causes too great a difference between desired idle and the actual idle speed will set a
DTC 35 or DTC 36.
DTC 35 (Idle Speed Low)
Or
DTC 36 (Vacuum Leak/ Idle Speed High) Either DTC will set if:
• No TP Sensor, IAT Sensor or VSS DTC’s are set.
• The engine has been running for at least 15 seconds.
• The IAT is less than 73°C.
• The engine s peed is 200 RPM below the desired idle speed for 5 seconds and the IAC has been opened to its
maximum position (255 steps), then a DTC 35 will set. If the PCM detects a condition where a high idle speed is
present and the IAC has been closed (0 steps); the PCM will comm and the IAC motor to open 50 steps. If the
RPM increases more than 50 RPM it is accepted that the IAC motor is moving and therefore the fault is a
vacuum leak , and DTC 36 will set. If the RPM does not c hange when the PCM commands the IAC to open, the
PCM will set DTC 36.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Value
There ARE no default values.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 35 AND 36 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED BATTERY VOLTAGE
TIME FROM START REFERENCE VOLTS
TIMES OCCURRED MASS AIR FLOW
IGNITION CYCLES CAM SIGNAL
COOLANT TEMPERATURE FUEL PUMP RELAY
Stall Data
If an engine stall occurs the PCM will capture nine data values. The PCM will store the first stall condition data
values, then count the number of stalls after the first.
NOTE: Stall data will be erased from the PCM memory whenever DTC HISTORY DATA is cleared.
STALL DATA
PARAMETER PARAMETER
ENGINE SPEED VEHICLE SPEED
TIME FROM START BATTERY VOLTAGE
TIMES OCCURRED THROTTLE ANGLE
IGNITION CYCLES A/C REQUEST
IDLE AIR CONTROL
Figure 6C2-1-79 IAC Valve Circuit
1.6 DIRECT IGNITION SYSTEM (DIS)
PURPOSE
The Direct Ignition System (DIS) system controls
fuel combustion by providing a spark to ignite the
compressed air/fuel m ixture at the correct time. To
provide optimum engine performance, fuel
economy, and control of exhaust emissions, the
PCM controls spark advance with the DIS system.
DIS has several advantages over a mechanical
distributor system:
• No moving parts.
• Less maintenance.
• Remote mounting capability.
• No mechanical load on the engine.
• More coil cool down time between firing events.
• Elimination of mechanical timing adjustments.
• Increased available ignition coil saturation time.
Legend:
1. Crankshaft Position (CKP) Sensor
2. Front Cover Stud (Three Places)
3. Crankshaft Balancer Assembly
4. Crankshaft Position Sensor Shield
4241
1
2
3
4
Figure 6C2-1-80 Crankshaft Sensor & Crankshaft Balancer
OPERATION
The Direct Ignition System (DIS) (1) is an ignition
system that does not use a conventional distributor
and ignition coil. The DIS ignition system consists
of; 3 ignition coils, a DIS module, a dual Hall-effect
crankshaft position sensor, an engine crankshaft
balancer with crankshaft sensor interrupter rings
attached to the rear, related connecting wires, and
the EST (electronic spark timing) portion of the
PCM. The PCM controls only the ignition timing and
dwell. The DIS c oils do the actual firing of the spar k
plugs.
Conventional ignition coils have one end of the
secondary winding connected to ground. In the
Direct Ignition System, neither end of the
secondary winding is grounded. Instead, each end
of a coil's secondary winding is attac hed to a spark
plug. These two plugs are on "companion"
cylinders, i.e., on top dead centre at the same time.
Legend:
1. Direct Ignition System Coil And Module Assembly
2. Powertrain Wiring Harness
3. Powertrain Wiring Harness Connector Screw
Figure 6C2-1-81 DIS Module And Coils
When the coil discharges, both plugs fire at the same time to complete the series circuit. The cylinder on
compression is said to be the `event' cylinder and the one on exhaust is the `waste' cylinder. The cylinder on the
exhaust strok e requires very little of the available energy to f ire the spark plug at idle. The r emaining energy will be
used as required by the cylinder on the compression stroke. This method of ignition is called "waste spark" ignition.
Since the polarity of the ignition coil primary and secondary windings is fixed, one spark plug always fires with a
forward current flow and it's `com panion' plug fires with a reverse curr ent flow. This is differ ent from a conventional
ignition system that fires all the plugs with the same direction of current flow.
Since it requires approximately 30% more voltage
to fire a spark plug with reverse current flow, the
ignition coil (‘1’, is one of three) design is im pr oved,
with saturation time and primary current flow (3)
increased. This redesign of the system allows
higher secondary voltage (2) to be available from
the ignition coils – greater than 40 kilovolts ( 40,000
volts) at any engine speed. T he voltage required by
each spark plug is determined by the polarity and
the cylinder pressure. T he cylinder on com pression
(4) requires more voltage to fire the spark plug
(approxim ately 8 k ilovolts) than the one on exhaust
(5) (approximately 3 kilovolts).
It is possible for one spark plug to f ire even though
a plug wire fed by the same coil may be
disconnected from its 'companion' spark plug
(‘companion’ cylinders are ; 1 & 4, 5 & 2, 3 & 6).
Legend:
1. Ignition Coil (One Of Three)
2. Secondary Coil
3. Primary Coil
4. Compression Stroke, TDC
5. Exhaust Stroke TDC
Figure 6C2-1-82 Waste Spark Ignition
(Companion Cylinders Have Pistons at TDC at the
Same Time)
The disconnected plug wire acts as one plate of a capacitor, with the engine being the other plate. These two
'capacitor plates' are charged as a spark jumps across the gap of the still-connected spark plug. The ‘plates' are
then disc harged as the sec ondary energy is diss ipated in an oscillating c urrent ac ross the gap of the s till-connec ted
spark plug. Secondary voltage requirements are very high with an 'open' spark plug or wire. The ignition coil has
enough reserve energy to fire the still-connected plug at idle, but possibly not under high engine load. A more
noticeable misfire may be evident under load; both spark plugs may be misfiring.
SYSTEM COMPONENTS
Crankshaft Sensor and Crankshaft Balancer Interrupter Rings
The dual crankshaft sensor, secured in an aluminium mounting bracket and bolted to the front left side of the engine
timing chain cover, is partially behind the crankshaft balancer. A 4-wire electrical harness connector plugs into the
sensor, connecting it to the DIS module.
The DIS dual crankshaft sensor contains two Hall-
effect switches with one shared magnet mounted
between them. The magnet and each Hall switch
are separated by an air gap.
A Hall switch reacts like a solid-state switch,
grounding a low-current signal voltage when a
magnetic field is present. When the magnetic field
is shielded from the switch by a piece of steel
placed in the air gap between the magnet and the
switch, the signal voltage is not grounded.
If the piece of steel (called an interrupter) is
repeatedly moved in and out of the air gap, the
signal voltage will appear to go "ON-OFF -ON-O FF-
ON-O FF." Com pared to a conventional mec hanical
distributor, this "ON-OFF" signal is similar to the
signal that a set of breaker points in the distributor
would generate as the distributor shaft turned and
the points opened & closed.
Legend:
1. Aluminium Mounting Bracket 2. 3X Air Gap
3. CKP Sensor 4. Magnet
5. Towards Crankshaft 6. 18X Air Gap
7. 3X Sensor 8. 18X Sensor
4
3
1
2
2
567
8
4244
Figure 6C2-1-83 – Crankshaft Position Sensor
In the case of the DIS system, not one but two
pieces of ‘s teel’, are two conc entric interr upter rings
mounted to the rear of the crankshaft balancer.
Each interrupter ring has blades and windows that,
with crankshaft rotation, either block the magnetic
field or allow it to reach one of the Hall switches.
The outer Hall switch is called the 18X-crankshaft
sensor, because the outer interrupter ring has 18
evenly spaced same-width blades and windows.
The 18X -crank shaft s ensor produces 18 "ON-OFF"
ground pulses per crankshaft revolution. The Hall
switch clos est to the cr anks haft, the 3X- crankshaft
sensor, is so called because the inside interrupter
ring has 3 unevenly spaced, different-width blades
and windows. The 3X-crankshaft sensor produces
3 different length "ON-OFF" ground pulses per
crankshaft revolution.
W hen a 3X interrupter ring 'window' is between the
magnet and inner switch, the magnetic field will
cause the 3X Hall switch to ground the 3X
crankshaft signal voltage supplied from the DIS
module. The 18X-interrupter ring and Hall switch
react similarly.
Figure 6C2-1-84 –
Crankshaft Balancer with Interrupter Rings
The DIS module interpr ets the 18X and 3X "ON-OFF" signals as an indication of crankshaft position, and must have
both signals to "f ire" the correc t ignition coil. T he DIS module determ ines c ranks haft position for cor rect ignition coil
sequencing by counting how many 18X-signal transitions occur, i.e. "ON-OFF" or "OFF-ON," during a 3X pulse.
It also uses thes e two signals to begin generating the Crank shaft Ref erence signal, which is the input s ignal for the
PCM to determine the crankshaft position and RPM.
A f ailure in the c r ank s haf t r ef er enc e signal input c irc uit to the PCM, will set a DTC 46. A failur e in the 18X r ef erenc e
signal circuit to the PCM, will set DTC 47.
Figure 6C2-1-85 – 18X and 3X Crankshaft Sensor Pulses for One Crankshaft Revolution
Legend
1. One 18 X Transition
2. Two 18 X Transitions 3. Three 18 X Transitions
4. 18 X Crankshaft Sensor Signal 5. 3 X Crankshaft Sensor Signal
6. One Crankshaft Rotation – 360°
1
10
23
4
5
6
6
º10
75 TDC
1 & 4
10 20
75 TDC
6 & 3
30
75 5 & 2
TDC
º
º
ºº
º
º
º
4245
Figure 6C2-1-86 – 18X & 3X Crankshaft Sensor Pulses and Crankshaft Reference Signal sent to the PCM
Legend
1. One 18X Transition
2. Two 18 X Transitions 3. Three 18 X Transitions
4. 18 X Crankshaft Sensor 5. 3 X Crankshaft Sensor
6. Crankshaft Reference Signal (Sent to PCM)
7. One Crankshaft Rotation – 360°
DTC 46 (No Reference Pulses While Cranking) will set if:
• No MAF sensor DTC is set.
• Battery voltage is at or below 11 volts.
• The MAF sensor input signal is greater than 2048 Hz.
• No crank shaft r eference input puls es are received at the PCM c ranks haft refe rence input term inal for at least 2
seconds.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Value
There are no default values for the crankshaft reference signal as the PCM uses this signal to determine if the
engine is running and initiate injection pulses. The engine will not run if the PCM does not receive a crankshaft
reference signal. With no crankshaft reference signal the PCM will not issue any injection pulses.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 46 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED BATTERY VOLTAGE
TIME FROM START REFERENCE VOLTS
TIMES OCCURRED MASS AIR FLOW
IGNITION CYCLES CAM SIGNAL
COOLANT TEMPERATURE FUEL PUMP RELAY
DTC 47 (18X Reference Signal Missing) will set if:
• The engine is running.
• The MAF sensor input signal is greater than 2048 Hz.
• The PCM detects 253 crankshaft reference pulses and no 18X pulses.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Value
When DTC 47 is set and current (no 18X reference signal), the PCM uses the crankshaft reference signal to
determine engine speed. This condition will cause the EST to be degraded; no high resolution spark.
Recovery
Recovery will occur when the PCM sees a valid condition.
1
10
23
4
5
6
7
º10
75 TDC
1 & 4
10
100 20
75 TDC
6 & 3
90 30
75
110
60
60
5 & 2
TDC
º
º
º
ºº
º
ºº
º
º
º
º
60
º
60
º
60
º
60
º
4246
DTC 47 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED COOLANT TEMPERATURE
TIME FROM START BATTERY VOLTAGE
TIMES OCCURRED REFERENCE VOLTS
IGNITION CYCLES INJECTOR VOLTAGE
Ignition Coils
Three twin-tower ignition coils (2) are individually
mounted to the DIS m odule (3), with six screw type
fasteners (1). Each coil provides the spark for two
spark plugs simultaneously (waste spark
distribution) and all three coils can be replaced
individually. Spade type electrical term inals connec t
each coil to the DIS module (3).
Three of the six terminals are connected together
by a circuit in the DIS module, supplying +12 volts
to the prim ary windings of all three coils. T he other
three terminals are individually connected to the
DIS module, so that the DIS module can control
only one c oil firing at a tim e, in the c orrec t order, by
removing the primary circuit ground path at the
proper time.
Figure 6C2-1-87 Ignition Coils & Ignition Module
Figure 6C2-1-88 Computer Controlled Coil Ignition
DIS Ignition Module
The DIS module serves several functions:
• It powers the dual crankshaft sensor internal circuits.
• It supplies the 3X and 18X voltage signals that each res pective Hall switch puls es to ground to gener ate the 3X
and 18X crankshaft sensor pulses.
• It determines the correct ignition coil firing sequence, based on how many 18X transitions occur during a 3X
pulse. This coil sequencing occurs at start-up. After the engine is running, the module remembers the
sequence, and triggers the proper ignition coil.
• It sends a "crank shaft r eference" s ignal to the PCM. The PCM interprets engine RPM f rom this signal. It is also
used by the PCM to determine crankshaft position for EST spark advance calculations. (The falling edge of
each c ranks haf t referenc e signal puls e occ ur s 70° bef or e TDC of any cylinder .) The cr ank s haf t r ef er ence s ignal
sent to the PCM by the DIS module is an "on-off" pulse occurring 3 times per crankshaft revolution. This is
neither the 3X nor the 18X-crankshaft sensor pulse, but both of these are required by the DIS module to
generate the crankshaft reference signal.
The DIS module generates the crankshaft reference signal by an internal "divide-by-6" circuit. This divider circuit
divides the 18X crankshaft sensor pulses by 6. The divider circuit is enabled, or ready to begin dividing, only
after it receives 3X crank shaft sensor pulses. After it receives the first 3X-crankshaft sensor signal, the divider
circuit does not need the 3X puls es to c ontinue oper ating. If either the 18X or 3X pulses ar e miss ing, the divider
cannot generate any crankshaft reference signal pulses (sent to the PCM), and no fuel injector pulses will
occur.
• Below 450 engine RPM (or anytime the PCM does not apply 5 volts to the DIS m odule 'bypass' circuit), the DIS
module controls ignition by triggering each of the three coils in the proper sequence at a predetermined dwell,
with spark advance fixed at 10 degrees BTDC. This is called bypass mode ignition. The DIS module provides
proper ignition coil sequencing during both the bypass and EST modes.
• Above 450 RPM, the PCM applies 5 volts to the DIS m odule 'bypas s' circuit, signalling the m odule to allow the
PCM to control the dwell and spark timing. This is EST mode ignition. During EST mode, the PCM adjusts
spark dwell and timing advance for all driving conditions. Again, the DIS module is responsible for proper
ignition coil sequencing during both the bypass and EST modes.
DIRECT IGNITION SYSTEM (DIS) NOTEWORTHY INFORMATION
There are important considerations to point out when servicing the Direct Ignition System. This "Noteworthy
Information" will list some of these, to help the technician in servicing the DIS system.
A. The ignition coils secondary voltage output capabilities are very high - more than 40,000 volts. Avoid body
contact with DIS high voltage secondary components when the engine is running, or personal injury
may result!
B. The dual Hall-effect 18X – 3X crankshaft sensor is the most critical part of the DIS system. If the crankshaft
sensor is damaged so that the 18X or 3X crankshaft sensor pulses are not generated, the engine will not start!
C. There are 4 circuit wires connecting the dual crankshaft sensor to the DIS module. If there is a problem with any
of the four, the engine will not start (No spark and no injector pulses). The circuits are:
• +10-to-12 volt operating power supply for the Hall switches from the DIS module.
• 18X sensor pulse signal to the DIS module.
• 3X sensor pulse signal to the DIS module.
• Ground circuit for both Hall switches.
• Equally important (for the engine to run) is the crankshaft reference signal generated by the DIS module,
sent to the PCM. If the PCM does not receive this signal, it will not pulse the fuel injectors.
D. If the 3X crankshaft sensor pulses cease while the engine is running; the engine will stop running and will not
restart.
E. If the 18X cranks haft sensor puls es cease while the engine is running; the engine will stop running and will not
restart.
F. The crankshaft sensor is not adjustable in its aluminium mounting bracket.
G. Ignition timing is not adjustable. Clearance of the crankshaft sensor is only for proper clearance of the rotating
interrupter rings in the sensor air gap, and does not affect ignition timing. There are no timing marks on the
crankshaft balancer or timing chain cover.
H. If c ranks haft sensor replacem ent is necess ary, the c ranks haft balancer m ust be removed f irst. The balancer is
a press fit onto the crankshaft and must be removed with a special tool; removing the serpentine accessory
drive belt, balancer and crankshaft sensor shield will allow access to replacing the crankshaft sensor. When
reinstalled, tightening the balancer attachment bolt to the correct torque specification, is critical to ensure the
balancer stays attached to the crankshaft.
I. If a crankshaft sensor assembly is replaced, 2 items are very important:
1. Check the crankshaft balancer interrupter rings for any blades being bent (runout and concentricity). If this
is not checked c losely and a bent blade exists, a new crankshaf t s ens or c an be des troyed by the bent blade
with only one revolution of the crankshaft!
2. The proper crankshaft sensor replacement procedure must be followed Refer to Section 6C2-3
SERVICE OPERATIONS for proper replacement procedure. This procedure will position the interrupter
rings in the centre of the sensor air gaps.
J. Neither side of the ignition coil primary or secondary windings is connected to engine ground.
K. Be c ar ef ul not to damage the high tens ion leads or boots (dus t c aps ) when ser vicing the ignition s ystem. Rotate
each boot to dislodge it from the plug or coil tower bef ore pulling it from either a spark plug or the ignition coil.
Never pierce a high tension lead or boot for any testing purposes! Future problems are guaranteed if
pinpoints or test lights are pushed through the insulation for testing.
L. The DIS module is grounded to the engine block through 2 mounting studs used to secure the module to it's
mounting br acket. If servicing is required, ens ure that good electrical contac t is m ade between the module and
its mounting bracket, including proper hardware & torque.
M. A c onventional tac hom eter used to c heck RPM on a prim ar y ignition 'tacho lead' will not work on DIS. To c heck
RPM, use one of the following methods:
• A tachometer designed with an inductive pick-up, used on the secondary side of an ignition system.
• These tachometer s are identified by a 'clamp' that goes around a spark plug wire. Set the tacho to '2-cycle'
operation. The reason for 2 cycle? Spark plugs on this engine fire every time the piston is at the top of its
stroke. If a '2 cycle' selection is not available, divide the indicated 4 cycle reading by 2.
• Tech 2 scan tool. Use "Engine Speed" display to read actual RPM.
1.7 ELECTRONIC SPARK TIMING (EST)
The V6 Direct Ignition System uses the same four ignition module to PCM circuits, as do all other Delco engine
management systems. They are:
• Crankshaft Reference PCM Input
• Crankshaft Reference Ground
• Bypass Control
• EST Output
In addition to these four circuits, the PCM used with this engine, also has the following two circuits:
• An 18X reference input used for High Resolution Spark Timing.
• A camshaft reference input used for sequential fuelling.
Electronic Spark Timing is the PCM's method of controlling spark advance and ignition dwell, when the ignition
system is operating in the EST mode.
There are two "modes" of ignition system operation:
• Bypass mode
• EST mode
In the bypass mode, the ignition system operates independently of the PCM, with bypass mode spark advance
always at 10 degrees BTDC. The bypass mode is in effect when cranking the engine. The PCM has no control of
the ignition system when in this mode. In fact, the PCM could be disconnected and removed from the car and the
ignition system would still f ire the spar k plugs while crank ing, as long as the other ignition system com ponents were
functioning! (This would provide spark but no fuel injector pulses, and a no-start.)
After the engine starts (RPM greater than 450), the PCM will cause the ignition system to change over to the EST
mode. Once the change is made to EST mode, it will stay in effect until either:
1. The ignition key is turned "OFF,"
2. The engine quits running, or
3. An EST fault is detected.
If an EST f ault is detected while the engine is running, the ignition s ystem will switch back to the bypass m ode. T he
engine may quit running, but will restart and stay in the bypass mode.
Figure 6C2-1-89 Cranking Below 450 RPM
Figure 6C2-1-90 Engine Running Above 450 RPM
Figure 6C2-1-91 Engine Running with EST Inputs
In the EST mode, the ignition spark timing and ignition dwell time are fully controlled by the PCM. EST spark
advance and ignition dwell are calculated by the PCM using the following inputs:
• Engine Speed (Crankshaft Reference).
• Crankshaft Position (Crankshaft Reference).
• Engine Load (MAF).
• Engine Coolant Temperature (ECT).
• Throttle Position (TP Sensor).
• Park/Neutral (TFP).
• Detonation (Knock Sensor).
• Vehicle Speed (VSS).
• Diagnostic Request Input (DLC diagnostic test terminal).
• PCM Power Supply.
The following describes the four PCM-to-ignition module circuits.
Crankshaft Reference PCM Input.
From the ignition module, the PCM uses this signal to calculate engine RPM and crankshaft position. The PCM
compares pulses on this circuit to any that are on ground crankshaft reference low circuit. T he PCM also uses the
pulses on this circuit to initiate injec tor pulses. If the PCM receives no pulses on this c ircuit, no fuel inj ection pulses
will occur, the engine will not run, and DTC 46 will set when attempting to start the engine.
Crankshaft Reference Ground.
This is a ground circ uit for the digital RPM counter inside the PCM, but the wire is connected to engine ground only
through the ignition m odule. Although this circuit is elec trically connec ted to the PCM, it is not connected to ground
at or through the PCM. T he PCM com pares voltage pulses on the r efer ence input circ uit to any on this circuit. If the
circuit is open, or connec ted to ground at the PCM, it may cause poor engine performance and c aus e a Malf unc tion
Indicator Lamp to be activated, with no DTC.
Bypass Control.
The PCM either allows the ignition m odule to keep the spark advance at "bypass mode" 10 degrees BTDC, or the
PCM signals the ignition module that the PCM is going to control the spark advance (EST mode). The ignition
module switches between the two m odes by the level of voltage that the PCM sends to the ignition module on the
bypass control circuit. The PCM provides 5 volts to the ignition m odule if the PCM is going to control spark tim ing
(EST m ode). If the PCM does not turn "ON" the 5 volts, or if the ignition module doesn't r eceive it, then the m odule
will keep control of spark tim ing (bypass mode). An open or grounded bypass control circuit will set a DTC 42 and
the ignition system will stay in 'bypass mode'. If the bypass control circuit is shorted to voltage then DTC 41 will set.
EST Output
The EST output circuitry of the PCM sends out timing pulses to the ignition module on this circuit. When in the
"bypass mode," the ignition module grounds these pulses. When in the EST mode, these pulses are the ignition
timing pulses used by the ignition module to energise the ignition coil. If the EST output circuit is open when the
engine is started, a DTC 41 will set and the ignition system will stay in the bypass mode. If this circuit becomes
shorted to voltage or grounded during EST mode operation above 1600 RPM, then DTC 42 will set.
HOW DTC 41 AND DTC 42 ARE DETERMINED
The EST output circ uitry in the PCM issues EST output pulses anytime c rank shaf t ref erence signal input pulses are
being received. When the ignition system is oper ating in the bypass m ode ( no voltage on the bypass control circ uit),
the ignition module grounds the EST pulses sent from the PCM. The ignition module will remove the ground path for
the EST pulses only after switching to the EST mode. (T he PCM comm ands the switching between bypass & EST
modes, via applying 5 volts on the bypass control circuit to the ignition module.)
The PCM has voltage monitors on the EST output line and the bypass control line. The PCM monitors it's EST
output, and expects to detect no EST pulses on the EST circuit when it has not supplied the 5 volts on the bypass
control circuit. W hen the RPM for EST operation is reached (approximately 450 RPM), the PCM applies 5 volts to
the bypass control circuit, and the EST pulses should no longer be grounded by the ignition module. The PCM
constantly monitors it's EST output, and should 'detect' the high EST pulses only when in the 'EST mode.'
If EST output circuit is open, the PCM will detect EST output pulses while attem pting to start the engine (in the
bypass mode) due to the ignition module not being able to ground the EST pulses. The PCM will check for this
condition during engine cr anking. Thr ee things will occur: 1. A DT C 41 will set, 2. T he PCM will not apply 5 volts to
the bypass control circuit, and 3. The engine will start and run in the bypass mode.
If EST output circuit is grounded or shorted to v oltage, the PCM would not detect a problem until the change to
EST mode happens. W hen the PCM applies 5 volts to the bypass control circuit, the ignition module will switch to
the EST mode. With EST circuit grounded or shorted to voltage, there would be no EST pulses for the ignition
module to trigger the ignition coil with, and the engine may falter. The PCM will quickly revert back to the bypass
mode (turn "OFF" the 5 volts on the bypass control circuit), DTC 42 will set, after the engine speed exceeds 1600
RPM. The ignition s ystem will operate in the bypass mode until the f ault is corrected and the engine is stopped and
restarted.
If bypass control circuit is open OR grounded, the ignition module can not switch to the EST mode. In this c ase,
the EST pulses will stay grounded by the ignition module, and DTC 42 will be set after the engine speed exceeds
1600 RPM. The engine will start and run in the bypass mode.
If bypass contro l circuit is shorted t o voltag e, the ignition m odule will be switched to the EST m ode all the time.
In this c as e, the PCM would detec t voltage on the bypass circuit only with the engine cranking and s et DT C 41. The
engine would start and run in the EST mode.
RESULTS OF INCORRECT OPERATION
An open or ground in the EST or bypass circuit will set a DTC 41 or DTC 42. If a fault occurs in the EST output
circuit when the engine is r unning, the engine may falter or quit running but will restart and run in the bypass mode.
A fault in either circuit will force the ignition system to operate on bypass mode timing (10 degrees BTDC), which will
result in reduced performance and fuel economy.
The PCM us es infor mation f r om the MAF and c oolant temperatur e s ensor s in addition to RPM to calc ulate the main
spark advance values as follows:
High RPM....................................................= more advance
Low MAF frequency (Low engine load).......= more advance
Cold engine .................................................= more advance
Low RPM.....................................................= less advance
High MAF frequency (High engine load) .....= less advance
Hot engine ..................................................= less advance
Therefore, detonation could be caused by incorrect low MAF output frequency or incorrect high resistance in the
coolant temperature sensor circuit. Poor performance could be caused by incorrect high MAF output frequency or
incorrect low resistance in the coolant temperature sensor circuit.
DTC 41 (Ignition Electronic Spark Timing Output Circuit Fault) will set if:
• The ignition is ON.
• The PCM has detected at least 2 EST output pulses during the first 3 crankshaft reference pulses received from
the ignition module.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
DTC 42 (Ignition Bypass Circuit Fault) will set if:
• The engine is cranking or running.
• The PCM has commanded EST.
• The PCM has detected no EST output pulses for 400 ms.
• The engine RPM is greater than 1600 RPM.
• The PCM will illuminate the Malfunction Indicator Lamp (MIL).
Default Values
When either DTC 41 or 42 are set, the PCM will operate in the Bypass spark mode.
Recovery
Recovery will occur on the next ignition cycle.
DTC 41 AND 42 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED COOLANT TEMPERATURE
TIME FROM START REFERENCE VOLTS
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES SPARK MODE
Figure 6C2-1-92 – Ignition System
1.8 ELECTRONIC SPARK CONTROL (ESC) SYSTEM
PURPOSE
Varying octane levels in today's petrol may cause
detonation in some engines. Detonation is caused
by an uncontrolled pressure in the combustion
cham ber . T his unc ontrolled pr es sur e could produce
a flam e f r ont oppos ite that of the normal flam e f r ont
produced by the spark plug.
The "rattling" sound normally associated with
detonation is the result of two or more opposing
pressures (flame fronts) colliding within the
combustion chamber. Though "light" detonation is
sometimes considered normal, "heavy" detonation
could result in engine damage. Light detonation
occurs when the point of maximum pressure has
been exceeded.
To c ontrol spark knoc k, a Knoc k Sensor (KS) (1) is
used. This system is designed to retard spark
timing up to 15 degrees to reduce spark knock in
the engine. T his allows the engine to use max imum
spark advance to improve driveability and fuel
economy.
1
4252
Figure 6C2-1-93 Knock Sensor
OPERATION
The ESC system has two major components:
• Knock Sensor Module (part of PCM).
• Knock Sensors (2).
The knock sensor detects abnormal mechanical vibration (spark knocking) in the engine. There are several
calibrations of knoc k sens ors becaus e each engine produces a diff erent frequenc y of mec hanical noise. The knock
sensor is specifically chosen for this engine to best detect engine knock, over all the other noises in the engine. This
engine has two knock sensors. Each sensor is mounted in the engine block near each bank of cylinders to better
detect detonation.
Figure 6C2-1-94 – Knock Sensor Locations
Legend
1. Left Hand Knock Sensor
2. Knock Sensor Shield LHS
3. Attaching Bolts
4. Wiring Harness Connector
5. Knock Sensor Shield RHS.
6. Right Hand Knock Sensor
7. Wiring Harness Connector
8. Attaching Bolts
Under a no knock condition, each circuit should
measure about 32 mV AC. The knock sensors
produce an AC output voltage that increases with
the severity of the knock, created by the piezo
crystal (1) and conditioned by a shunt resistor (2).
This signal voltage inputs to the PCM. This AC
signal voltage to the PCM is processed by an
analog signal to a Signal Noise Enhancem ent Filter
(SNEF) module.
This SNEF module is used to determine if the AC
signal coming in is noise or actual detonation. This
SNEF module is part of the PCM and cannot be
replaced. The processed knock sensor signal is
then supplied to the PCM. The PCM then adjusts
the ignition control system to reduce the spark
advance.
How much the timing is retar ded, is based upon the
amount of time k noc k is detec ted and is limited to a
max im um value of 15 degr ees. Af ter the detonation
stops, the timing will gradually return to it's
calibrated value of spark advance.
The Knock Sensor system will only retard timing
after the following conditions are met:
• Engine running longer than 5 seconds.
• Battery voltage higher than 9.3 Volts.
• Engine speed above 550 RPM.
• ECT greater than 45° C.
1
2
4254
Figure 6C2-1-95 Knock Sensor Sectioned View
The T ech 2 scan tool has two data displays to check for diagnosing this k nock sensor c ircuit. "KNOCK SIGNAL" is
used to monitor the input signal from the knock sensors. This position will display "YES" when knock is being
detected. "KNOCK RETARD" is the indication of how much the PCM is retarding the spark advance.
The Knock Sensor System has two DTC's to detect a failure in its system. DTC 43 is designed to diagnose the
knock sensor and wiring, so that problems encountered with this circuit should set the DTC. The PCM learns a
minimum noise level from the knock sensors.
• The actual noise level is determined as:
Noise level = Filtered Noise - Minimum Noise.
If the noise level is too low or too high then DTC 43 will be set.
The second DTC associated with the Knock Sensor is DTC 93. DTC 93 indicates that the engine has been
detonating longer than norm al. The PCM monitors the output of the SNEF circuit. W hen the SNEF output signal is
significantly longer than the longest expected “normal" output, it is assumed that the SNEF circuitry has failed and
DTC 93 is set.
DTC 43 (Knock Sensor Circuit) will set if:
• No DTC 14,15,16,17,19 ,21, 22, or 93 are set.
• Engine has been running longer than 10 seconds.
• Engine Coolant Temperature is greater than 65 °C.
• TP sensor signal is greater than 22%.
• Engine RPM is between 2000 and 6375 RPM.
• There is no knock sensor signal or too high a knock sensor signal detected by the PCM for 3 seconds
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
DTC 93 (Knock Sensor System) will set if:
• The engine has been running for more than 10 seconds.
• The PCM’s SNEF circuit indicates knocking for more than 10 seconds.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
Once DTC 43 OR 93 is set, and current, the PCM uses a default spark advance table.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 43 AND 93 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED MASS AIR FLOW
TIME FROM START KNOCK DETECTION
TIMES OCCURRED INTAKE AIR TEMPERATURE
IGNITION CYCLES SPARK ADVANCE
COOLANT TEMPERATURE THROTTLE ANGLE
Figure 6C2-1-96 - Knock Sensor Wiring
1.9 EVAPORATIVE EMISSION
The Evaporative Emission Control System (EECS)
used on this vehicle is the charcoal canister
storage method. T his method tr ansfers f uel vapour
from the fuel tank, via piping and port (2) to an
activated carbon (charcoal) storage device
(canister located under the rear of the vehicle) to
hold the vapour s when the vehicle is not operating.
When the engine is running, the fuel vapour is
purged f r om the c ar bon element through por t (1) by
intake air flow through port (3) and consumed in the
normal combustion process.
The EECS purge solenoid valve allows manifold
vacuum to purge the canister, via port (1). The
Powertrain Control Module (PCM) supplies an
ground s ignal to energise the EECS purge s olenoid
valve (purge “ON”). The EECS purge solenoid
control is Pulse W idth Modulated (PW M) or turned
“ON” and “ OFF” several tim es a second. T he PCM
controlled PWM output is commanded when the
appropriate conditions have been met:
• Engine coolant temperature above 80°C.
• Engine has been running longer than 3
minutes.
• Engine is not in Decel Fuel Cutoff Mode.
• Throttle opening is less than 92%.
• Engine is in Closed Loop mode.
3
1
2
4255
Figure 6C2-1-97 – Fuel Vapour Canister
EECS purge PWM duty cycle varies according to
operating conditions determined by mass air flow,
fuel trim and intake air temperature. The EECS
purge will be re-enabled when TP angle decreases
below 92%.
The canister (located under the rear of the vehicle)
cannot be repaired, and is serviced only as an
assembly. Periodically check the canister at the
time or distance intervals specified in the vehicle
Owners Handbook. If there is a fault with the
Canister Purge Solenoid electrical circuits, DTC 97
will set.
Legend:
1. To Throttle Body
2. To Canister
3. Solenoid Valve
4. Solenoid Mounting Bracket Screw
5. Solenoid Mounting Bracket
Figure 6C2-1-98 – Canister Purge Solenoid Location
The fuel vapour canister (1) is mounted in a
bracket underneath the vehicle, near the fuel filter.
This canis ter is a three por t design. The fuel vapour
is absorbed by the charcoal within the canister.
When the engine is running at idle speed and
above idle, air is drawn into the canister through the
atmospheric port at the top of the canister
assembly. The air mixes with the fuel vapour and
the mixture is dr awn into the intak e manif old via the
canister purge line.
The upperm ost port on the c anister is controlled by
a PCM controlled canister purge solenoid. The
canister purge solenoid controls the manifold
vacuum signal from the throttle body. The port
below the canister purge port is the vapour inlet
from the fuel tank. The single off centre port is
open to the atmosphere.
Figure 6C2-1-99 – Canister Location
The evaporative canister consists of an air vent
port (1), a canister purge port (2), a port to receive
vapour from the fuel tank (3), the canister housing
(4), a dust filter (5) and the charcoal bed (6).
Figure 6C2-1-100 – Sectioned View of Canister
RESULTS OF INCORRECT OPERATION
• Poor idle, stalling and poor driveability can be caused by:
– Inoperative canister purge solenoid
– Damaged canister.
– Hoses split, cracked and/or not connected to the proper tubes.
• Evidence of fuel loss or fuel vapour odour can be caused by:
– Liquid fuel leaking from fuel lines.
– Cracked or damaged canister.
– Disconnected, misrouted, kinked, deteriorated or damaged vapour hoses, or control hoses.
If the solenoid is stuc k open, or the c ontrol circuit is shorted to ground the canis ter will purge to the intake m anif old
all the time . T his c an allow extra f uel at idle or dur ing warm-up, which c an caus e r ough or uns table idle or a rich fuel
operation.
If the canister purge solenoid is always closed, the canister can become over loaded with fuel, resulting in fuel
odour.
A failure in the canister purge solenoid or circuit may result in DTC 97.
DTC 97 (Canister Purge Circuit Fault) will set if:
• The ignition is ON.
• The PCM detects the incorrect voltage on the canister purge solenoid driver.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
There are no default values for DTC 97.
Recovery
Recovery will occur when the PCM sees a valid condition.
DTC 97 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED COOLANT TEMPERATURE
TIME FROM START PURGE PWM
TIMES OCCURRED MASS AIR FLOW
IGNITION CYCLES
Figure 6C2-1-101 – Typical Evaporative Emission Control Schematic
1.10 ELECTRIC COOLING FAN
Two, single speed engine c ooling fan motor s are used. One fan m otor is rated at 120 Watts ( Low Speed Fan) and
the other, at 160 Watts (High Speed Fan).
The fan motors are controlled individually by two relays, located in the underhood electrical centre (refer Fig
6C2-1-103). T he relays contr ol f an oper ation by switching the negative term inals of each motor to ground, while the
positive term inal of each m otor has a direct power f eed fr om two fusible link s, F 101 for the left f an and F107 for the
right.
The engine c ooling f an high s peed relay is controlled by the PCM. The PCM controls the gr ound path f or the engine
cooling fan high speed relay.
The low speed electric fan is controlled by the PCM through the serial data bus, Normal Mode Message to the BCM.
The BCM controls the ground path for the engine cooling fan low speed relay. The engine cooling fan high speed
relay and the engine cooling fan low speed relay are used to control the ground signal to the electric motors that
drive the equally spaced, eight bladed fans.
The PCM determ ines operation of the two engine cooling fans, bas ed on A/C request, engine coolant tem perature,
A/C Refrigerant Pressure Sensor, and vehicle speed signal inputs.
Figure 6C2-1-102 – Cooling Fans, V6 Engine Standard Specification
Legend
1. Fan Shroud
2. Radiator
3. Fan Shroud Lower Support
4. Fan Shroud Upper Support/Locking Retainer
5. Left Fan – 8 Blade, 370 mm Diameter
6. Left Fan Motor – 160 Watt, Single Speed
7. Left Fan Motor Securing Screws (3 places)
8. Left Fan Motor Harness Connector (2 terminal)
9. Power Steering Reservoir Mount
10. Left and Right Fan Motor Harness Connector (6 terminal)
11. Right Fan – 8 Blade, 268 mm Diameter
12. Right Fan Motor – 120 Wa tt, Single Speed
13. Right Fan Motor Securing Screws (3 places)
14. Automatic Transmission Fluid Cooler Line Retaining Clips
There ar e als o s uppres s ion c apac itors inc orpor ated into the f an motor wiring circuits . These s uppres s ion capac itors
help eliminate f an motor noise through the radio speakers. If these capacitors are open, then noise will be present
through the radio speakers. If shorted to ground, the fan m otors could continuously run, or the fuse or fusible link
could fail.
ENGINE COOLING FAN LOW SPEED
The engine cooling fan low speed relay (1) is
energised by the BCM. The PCM determ ines when
to enable the low speed fan based on inputs from
the BCM serial data, Engine Coolant Temperature
(ECT) sensor and the Vehicle Speed Sensor
(VSS).
The c ooling fan low speed re lay will be turned "ON''
when:
• The A/C request indicated (YES) and either:
• The vehicle speed is less than 30 km/h,
or
• The coolant temperature is greater than
104° C.
• If the coolant temperature is greater than
117° C when the ignition is switched off, the
relay is energised for up to approximately 4
minutes.
• If an engine coolant tem per ature sens or f ault is
detected, such as DTC 14, 15, 16, or 17.
Figure 6C2-1-103 Cooling Fan Low Speed Relay Location
The cooling fan low speed relay will be turned "OFF'' when any of the following conditions have been met:
• The A/C request is not indicated (NO)
• Engine coolant temperature is less than 99° C.
The A/C request is indicated (YES) and the vehicle speed is greater than 50 km/h and A/C pressure is less than
1,170 kPa.
LOW SPEED RESPONSE
The engine cooling low speed fan is enabled when the low speed relay is energised by the BCM. The PCM will
request the BCM to turn the low speed engine cooling fan relay on or off, via the serial data bus Normal Mode
Message. After the PCM requests a change in the engine cooling fan low speed relay, the BCM will send a
response message back to the PCM via the serial data bus Normal Mode Message confirming it received the
request. A failure in the response communication will set a DTC 92.
DTC 92 (Low Speed Fan – No BCM Response) will set if:
• Engine is idling
• The PCM sends a request to the BCM to turn ON the engine cooling fan low speed relay via the serial data
normal mode message and the BCM does not send a message back to the PCM.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
Once DTC 92 is set, the PCM will energise the engine cooling fan high-speed relay
Recovery
Recovery will occur on the next ignition cycle.
DTC 92 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED REFERENCE VOLTS
TIME FROM START MASS AIR FLOW
TIMES OCCURRED CAM SIGNAL
IGNITION CYCLES FUELLING MODE
COOLANT TEMPERATURE FUEL PUMP RELAY
BATTERY VOLTAGE
Figure 6C2-1-104 – Engine Cooling Fan Circuit
ENGINE COOLING FAN HIGH SPEED
The engine cooling fan high speed relay (2) is
controlled by the PCM, based on input from the
Engine Coolant Temperature (ECT) sensor. The
PCM will only turn “ ON’’ the engine cooling fan high
speed relay if the engine cooling fan low speed
relay has been “ON” for 2 seconds and the
following conditions are satisfied.
• There is a BCM mes s age res pons e f ault, which
will cause a DTC 92.
• An engine coolant temperature sensor fault is
detected such as DTC 14, 15, 16, or 17.
• Coolant temperature greater than 107° C.
• The engine cooling fan high speed relay (2)
can also be enabled by the A/C Refrigerant
Pressure Sensor. When the PCM determines
the A/C system pressure is too high (greater
than 2,600 kPa), it will enable the high speed
fan.
NOTE:If the low speed fan was "OFF" when the
criteria was met to turn the high speed fan "ON",
the high speed fan will com e "ON" 5 seconds after
the low speed fan is turned "ON".
If both the engine cooling fan relays are "ON", the
PCM will turn "OFF" the high speed relay when:
• The engine coolant temperature is less than
108° C.
• A/C request not indicated (NO).
• A/C request indicated (YES) and A/C pressure is
less than 2,300 kPa.
There ar e no DTC’s as soc iated with the high speed
cooling fan relay.
Figure 6C2-1-105 Cooling Fan High Speed Relay Location
1.11 A/C CLUTCH CONTROL
This vehicle can be fitted with two different types
of A/C clutch control. One type is standard A/C
(Figure 6C2-1-106) and the other uses an HVAC
Occupant Climate Control (OCC) module (Figure
6C2-1-107).
With the OCC system, when the A/C is requested,
the Electronic Climate Control Module will then
send a serial data request to the PCM. W hen the
PCM receives the serial data request on PCM
terminal X1 A3, it indicates that air conditioning
has been requested and approximately 1/2
second after the PCM receives this signal, it will
provide a ground circuit through X3 F4 for circuit
459 (L-G N/BK). The s erial data signal to the PCM
is also used to adjust the idle speed before
turning "ON" the A/C compressor relay. If this
signal is not available to the PCM, the A/C
compressor will be inoperative.
The BCM also supplies the ground signal from
BCM terminal X1 15 to the low speed cooling fan
relay (‘1’ in Figure 6C3-1-103).
This A/C system also incorporates an A/C
Refriger ant Pres s ure Sens or. The A/C Ref riger ant
Pressure Sensor signal indicates high side
refrigerant pressure to the PCM. The PCM uses
this information to adjust the idle air control valve
to compensate for the higher engine loads
present with high A/C refrigerant pressures and
also for electric engine cooling f an control. A fault
in the A/C Refrigerant Pres sure Sensor signal will
cause DTC 96 to set.
Figure 6C2-1-106 – A/C Relay Location
The PCM will NOT energise the A/C control relay if any of the following conditions are present:
• Coolant temperature is above 119°C. Once coolant temperature is below 116°C, A/C is reactivated.
• RPM more than 5,800. If de-energised because of RPM, it can be re-energised when RPM falls below 5,400.
• Throttle is m ore than 96% open. When de-ener gised during wide-open throttle, it will be re-energis ed when the
throttle is less than 92% open.
On vehicles equipped with non-OCC systems, the power flow is different. W ith the blower fan switched "ON", and
the air conditioning switched "ON," switched ignition voltage is supplied from fuse F13 through the A/C master
switch, and then to the BCM. The BCM will then supply a serial data signal to the PCM requesting A/C. If the BCM
does not receive a ground signal from the blower switch to BCM terminal X3 9, the BCM will not supply the serial
data request for A/C. Once the PCM receives this serial data signal, the PCM will energise the A/C compressor
relay. The BCM also supplies the ground signal from BCM terminal X1 15 to the low speed cooling fan relay.
This serial data signal to the PCM is also used to adjust the idle speed before turning "ON" the A/C compressor
relay. If this signal is not available to the PCM, the A/C compressor will be inoperative.
As on the OCC system, this one also incorporates an A/C Refrigerant Pressure Sensor. The A/C Refrigerant
Pressure Sensor signal indicates high side refrigerant pressure to the PCM. The PCM uses this information to
adjust the idle air control valve to compensate for the higher engine loads present with high A/C refrigerant
pressures, as well as for electric engine cooling fan control. A fault in the A/C Ref rigerant Pressure Sensor signal
will cause DTC 96 to set.
There are no DTC’s associated with A/C system except for the A/C Refrigerant Pressure Sensor DTC 96.
Figure 6C2-1-107 A/C Clutch Control with HVAC OCC
Figure 6C2-1-108 – A/C Clutch Control without HVAC OCC
1.12 A/C REFRIGERANT PRESSURE SENSOR
The A/C Refrigerant Pressure Sensor is a sealed
gauge reference capacitive pressure sensor with
on board signal conditioning. It provides a 0 to 5
Volt output and requires a 5 Volt regulated power
supply.
In operation, the Sensor senses applied pressure
via the deflection of a two piece c er amic diaphr agm
with one half being a parallel plate capacitor.
Changes in capacitance influenced by the
refrigerant pressure under the ceramic diaphragm
are converted to an analogue output by the
sensor’s integral signal electronics.
The pressure Sensor’s electronics are on a flexible
circuit board contained in the upper section of the
sensor. They provide linear calibration of the
capacitance signal from the ceramic sensing
diaphragm.
Benefits of using the pressure sensor over a
normal type pressure switch is that the sensor is
constantly monitoring pressures and sending
signals to the Powertrain Control Module (PCM).
The norm al type pressure s witch only has an upper
and lower cut-out point. The PCM will disengage
the A/C compressor at Low or High refrigerant
pressures and control the operation of the engine
cooling fans.
Legend
1. A/C Pressure Transducer
2. High Side Charge Port
3. Signal Electronics
4. Pressure Port
5. Ceramic Diaphragm
Figure 6C2-1-109 A/C Pressure Sensor Location and
Sectioned View
If there is a failure in the A/C Pressure Sensor circuit, DTC 96 will set.
Action Pressure OFF Pressure ON
Low Pressure Compressor Cut At 180 kPa At 240 kPa
High Pressure Compressor Cut At 2,900 kPa At 2,400 kPa
Engine Cooling Fan, High Speed At 2,600 kPa At 2,300 kPa
DTC 96 (A/C Pressure Sensor Circuit) will set if:
• Engine Coolant Temperature is below 119° C.
• Intake Air Temperature is below 90° C.
• Engine RPM is below 2000.
• Engine has been running for less than 10 minutes.
• A/C Refrigerant Pressure Sensor signal voltage is greater than 4.9 volts
• All of the above conditions are present for longer than 10 seconds.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
W hen DTC 96 is set, the low speed cooling fan will operate for five seconds, then the high speed fan will turn ON
and remain on until the fault is removed.
Recovery
Recovery will occur on the next ignition cycle.
DTC 96 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED ECT SENSOR
TIME FROM START IAT SENSOR
TIMES OCCURRED INTAKE AIR TEMPERATURE
IGNITION CYCLES BATTERY VOLTAGE
COOLANT TEMPERATURE REFERENCE VOLTS
REFERENCE VOLTS
Figure 6C2-1-110 A/C Refrigerant Pressure Sensor Circuit
1.13 S UP ERCHARGER SYSTEM
DESCRIPTION
The supercharger is a positive displacement pump that consists of two counter-rotating rotors in a housing with an
inlet port and an outlet port. T he r otors ar e designed with three lobes and a helical twist. An air bypass circ uit is built
into the housing. The rotors in the supercharger are designed to run at a minimal clearance, not in contact with each
other or the housing. The rotors are timed to each other by a pair of precision spur gears, which are pressed onto
the rotor shafts. The forward end of the rotors are held in position by deep groove ball bearings. The back end of
the rotors are supported by sealed roller bearings.
The gears and ball bearings are lubricated by synthetic oil. The oil reservoir is self-contained in the supercharger
and does not rely on engine oil for lubrication.
The c over on the superc harger c ontains the input shaf t, which is s upported by two deep groove ball bearings and is
coupled to the rotor drive gears. T hese bearings are lubricated by the synthetic oil contained in the sam e reservoir
as the gears and rotor bearings. The pulley is pressed and keyed onto the input shaft.
SUPERCHARGER OPERATION
The supercharger is designed to pump more air than the engine would normally use. This excess air creates a
boost pressure in the intake manifold. Maximum boost can range from 50 to 80 kPa (7 to 11 P.S.I.). Since the
superchar ger is a positive displacem ent pum p and is directly driven from the engine acc essory drive system, boost
pressure is available at all driving conditions.
When boost is not desired, such as during idle and light throttle cruising, the excess air that the supercharger is
producing is routed through the bypass passage between the intake manifold and the supercharger inlet. This
bypas s circuit is r egulated by a bypas s valve which is sim ilar to a throttle plate. The bypass valve is c ontrolled by a
vacuum actuator, which is connected to the vacuum signal between the throttle and the supercharger inlet. Spring
force from the actuator holds the valve closed to create boost and vacuum pulls the valve open when the throttle
closes to decrease boost. The open bypass valve reduces pumping loss thereby increasing fuel efficiency.
The Boost Control Solenoid valve is an electronically controlled valve. This valve, controlled by the PCM,
determines whether pressure from the manifold is routed to the bypass actuator or closed off. The solenoid allows
pressure from the manifold to open the bypass valve and regulate boost pressure during specific driving conditions.
BOOST CONTROL
The boost control system regulates induction boost press ure during r apid deceleration, under very high engine load
situations and anytime reverse gear is selected.
Figure 6C2-1-111 Supercharger Components
Legend
1. Lobes
2. Inlet Manifold
3. Boost Control Actuator and Valve
4. Throttle
5. Rotors
6. Timing Gears
OPERATION
Under most conditions, the PCM commands the
Boost Control Solenoid to operate at 100% duty
cycle ("ON"), keeping the solenoid valve closed and
allowing only inlet vacuum to control the position of
the Bypass valve.
At idle, full inlet vacuum is applied to one side of
the Bypass Valve Actuator diaphragm and
counteracts spring tension to hold the bypass valve
open. As the engine load increases, reduced
vacuum acts upon the spr ing tension in the Bypas s
Valve Actuator (1), causing the bypass valve to
close and increase boost pressure.
W hen reduced boost pressure is desired, the PCM
commands the Boost Control Solenoid to operate
at 0% duty cycle ("OFF"). This opens the solenoid
valve and allows boost pressure from the intake
manifold to counteract the spring tension in the
Bypass Valve Actuator, opening the bypass valve
and recirculating excess boost pressure back into
the supercharger inlet.
With reverse gear selected, the PCM commands
the Boost Control Solenoid to operate at 0% duty
cycle ("OFF") at all times.
Legend:
1. Bypass Valve Actuator
2. Throttle Body
4264
12
Figure 6C2-1-112 Bypass Valve Actuator
RESULTS OF INCORRECT OPERATION
An open Boost Control Solenoid driver circuit, ignition feed circuit, or Boost Control Solenoid valve stuck open will
cause reduced engine power, especially during wide open throttle operation.
The Boost Control Solenoid driver circuit shorted to ground, Boost Control Solenoid valve stuck closed or a
restriction in the boost source or signal hoses will cause full boost to be commanded at all times and a possible
overboost condition during high engine load situations.
A restriction in the vacuum signal hoses to the Bypass Valve Actuator or a stuck closed bypass valve will cause a
rough idle and reduced fuel economy.
DIAGNOSIS
The boost control system diagnosis is covered in Section 6C2-2, TABLE 2-6, in this Section. For further
information on the Supercharger and boost control system, and on vehicle service, refer to
Section 6C2-3 SERVICE OPERATIONS, in this Section.
Figure 6C2-1-113 Boost Control Solenoid Location
Legend
1. Boost Control Solenoid
Figure 6C2-1-114 – Boost Control System (Bypass Closed)
Legend
1. Boost Control Solenoid
2. Atmospheric Pressure Boost Signal Hose
3. Bypass Valve Actuator
4. Vacuum Source Hose
5. Throttle Butterfly
6. Bypass Valve (Closed)
7. Intake Manifold
8. Supercharger
9. Intake Manifold Pressure Signal
Figure 6C2-1-115 Boost Control System (Bypass Open)
Legend
1. Boost Control Solenoid
2. Atmospheric Pressure Boost Signal Hose
3. Bypass Valve Actuator
4. Vacuum Source Hose
5. Throttle Butterfly
6. Bypass Valve (Closed)
7. Intake Manifold
8. Supercharger
9. Intake Manifold Pressure Signal
Figure 6C2-1-116 Boost Control Solenoid Circuit
1.14 ANTILOCK BRAKING SYSTEM / TRACTION CONTROL SYSTE M
PURPOSE
The Traction Control System (T.C.S.) is designed
to maintain traction and reduce wheel over spin at
the drive wheels on slippery surfaces during
acceleration. This system is designed to operate at
all vehicle speeds and reduc es wheel slip by use of
the engine torque management system and Anti-
Lock Brake (ABS) system.
The ABS/TCS control module comprises the
ABS/TCS hydraulic modulator (1) and the
ABS/TCS c ontrol m odule ( 2). The ABS/T CS control
module (2) monitors both front and rear wheel
speeds through the wheel speed sensors. If at any
time during acceleration the ABS/TCS control
module detects drive wheel slip, it will request (on
the Torque Request circuit) the Powertrain Control
Module (PCM) to bring ex cess engine torque into a
specific range. This is accomplished via two high
speed Pulse Width Modulated (PWM) circuits
between the ABS/TCS control module and the
PCM. This is displayed on the scan tool as a Nm
value. The PCM will then adjust spark firing and
air/fuel ratio, and shutting "OFF" up to five (5)
injectors (if necessary), and report the modified
torque value (on the Actual Torque circuit) back to
the ABS/TCS control module in the form of a Nm
value. These Nm values should match closely
when traction control is being requested.
XT12L016
1
2
Figure 6C2-1-117 ABS/TCS Module Location
Simu ltaneous with engine torque managem ent, the ABS/TCS control m odule will activate the ABS isolation valves,
turn on the ABS pump motor and supply brake pressure to the over spinning wheel(s).
The isolation valves isolate the front brake hydraulic circuits from the master cylinder and rear brake hydraulic
circuits. Once the rear brake hydraulic circuits are isolated, pressure can be applied to the rear wheels without
affecting any other brake hydraulic circuits. The ABS/TCS control module turns on the ABS pump motor to apply
pressure, and begins cycling the ABS hydraulic modulator's inlet and outlet valves.
The inlet and outlet valve c ycling aids in obtaining m aximum road surf ace traction in the sam e manner as the Anti-
Lock Brak e m ode. T he diff erence between Electr onic T raction Contr ol and Anti-Lock Br ake mode is that brak e fluid
pressur e is inc reas ed to les s on wheel s pin (Trac tion Contr ol mode), r ather than r educ ed to allow greater wheel spin
(Anti-Lock Brake mode).
If at any time during T r ac tion Control mode, the br akes ar e manually applied, the brake switch s ignals the ABS/TCS
control module to disable Traction Control mode and allow manual braking.
If there is a malf unction with the Torque Request PWM c ircuit between the ABS/TCS contr ol module and the PCM,
DTC 95 will set. If there is a malfunction with the Actual Torque circuit between the ABS/TCS control module and
the PCM, an ABS/TCS DTC will set.
For further description on the Anti-Lock Brake System (ABS), and Traction Control System (TCS), Refer to
Section 5B ABS and ABS/TCS for information on ABS/TCS operation and DTC diagnosis.
DTC 95 (Requested Torque Out of Range) will set if:
• The engine is running.
• The PCM detects the incorrect voltage on the Requested Torque circuit.
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
Default Values
W hen DTC 95 is set, traction control will be disabled and a corresponding DT C will be set in the ABS/T CS control
module.
Recovery
Recovery will occur when the DTC has been cleared and the ignition cycled OFF and ON.
DTC 95 HISTORY DATA
PARAMETER PARAMETER
ENGINE SPEED TFT
TIME FROM START THROTTLE ANGLE
TIMES OCCURRED VEHICLE SPEED
IGNITION CYCLES COMMANDED GEAR
COOLANT TEMPERATURE
Figure 6C2-1-118 – Traction Control Circuit
1.15 ABBREVIATIONS AND GLOSSARY OF TERMS
Abbreviations used in this Volume are listed below in alphabetical order with an explanation of the abbreviation.
AC – ALTERNATING CURRENT – A current with varying magnitude.
A/C – AIR CONDITIONING
A/F – AIR/FUEL (A/F RATIO)
ANALOG SIGNAL – An electrical signal that varies in voltage within a given parameter.
BARO – BAROMETRIC PRESSURE – Atmospheric pressure. May be called BARO, or barometric absolute
pressure.
BAT – BATTERY – Stores chemical energy and converts it into electrical energy. Provides DC current for the
vehicle electrical systems.
CAT. CONV. – CATALYTIC CONVERTER – A muffler-shaped device fitted in the exhaust system, between the
engine and the muffler. It is the primary "workhorse" of the emission control system, and the PCM's control of the
air/fuel ratio allows it to operate efficiently. It contains platinum, palladium and rhodium. It receives pollutants (HC,
CO, and NOx) emitted by the engine, and through a chemical reaction, converts these harmful pollutants into
harmless water vapour, carbon dioxide, and nitrogen. Maximum conversion efficiency of exhaust emissions is
achieved with precise control of the air/fuel ratio at 14.7-1.
CCP - CONVERTER CANISTER PURGE – A PCM controlled solenoid to purge the charcoal canister.
CKT - CIRCUIT
CLOSED LOOP – A fuel c ontrol system m ode of operation that us es the signal f rom the exhaus t oxygen sensor, in
order to control the air/fuel ratio precisely at a 14.7 to 1 ratio, allowing maximum efficiency of the catalytic converter.
(CMP) CAMSHAFT POSITION SENSO R – The PCM uses this signal to determine the position of the No.1 piston in
its power stroke. This signal is used by the PCM to calculate sequential fuel injection mode of operation.
CO - CARBON MONOXIDE – One of the pollutants found in engine exhaust.
DC - DIRECT CURRENT – A current with a constant direction.
DTC - DIAGNOSTIC TROUBLE CODE – The PCM can detect malfunctions in the engine or transmission
management s ystem . If a malf unc tion oc cur s , the PCM may turn on the MIL, and a two-digit code number will set in
the PCM's m emory. A diagnostic tr ouble code can be obtained fr om the PCM, us ing Tech 2. T his DT C will indicate
the area of the malfunction and, by properly following the diagnostic procedures for the engine management
system, the problem source will be found.
DIGITAL SIGNAL – An electrical signal that is either one of two states, "ON" or "OFF" with no in between.
DLC – DATA LINK CONNECTOR – The 16 pin connector used at the assembly plant to evaluate the control
module system . T he c onnec tor is als o us ed in s ervic e to f lash the Malfunction Indic ator Lamp ( MIL). T his c onnector
is also used by Tech 2 to make system checks.
DLC DATA STREAM – An output of the PCM, initiated by the Tech 2 scan tool sending a command to the PCM.
This output is a digital com puter language signal, used by assem bly plant test equipment and the Tech 2 scan tool.
This signal is transmitted to the data link connector.
DRIVER – An electronic device, usually a power transistor, that operates like a switch; that is, it turns something
"ON" or "OFF."
DUTY CYCLE –- The measurem ent of the length of tim e, in percentage, that a circuit is "ON" versus "OFF" when
compared with a 100% full ON/OFF time factor.
DMM (10 Meg.) – Digital multimeter with 10 million ohms per volt impedance - used for voltage and resistance
measurement in electrical/electronic systems.
EECS – EVAPORATIVE EM ISSIONS CONT ROL SYSTEM – Used to prevent petr ol vapours in the fuel tank fr om
entering the atmosphere. Stores the vapours in a storage canister, located under the rear of the vehicle. Canister
contains activated charcoal, and the vapours are "purged" by engine vacuum during certain operating conditions.
EEPROM – ELECTRICALLY ERAS ABLE PROGRAMMABLE READ ONLY MEMORY – Type of read only
memory (ROM) that can be electrically programmed, erased and reprogrammed.
EMI or ELECTRICAL NOISE – An unwanted signal interfering with another needed signal; like an electric razor
upsets a television picture, or driving under high voltage power lines upsets the AM radio in a vehicle.
EGR – EXHAUST GAS RECIRCULATION VALVE – A device that is used to lower Oxides of Nitrogen (NOx)
emission levels by recirculating exhaust gases back into the combustion chamber.
ENGINE COOLANT TEMPERATURE (ECT) SENSOR – Device that s enses the engine coolant tem perature, and
passes that information to the powertrain control module.
EPROM – ERASABLE PROGRAMMABLE READ ONLY MEMORY – Type of read only memory (ROM) that can
be erased with ultraviolet light and reprogrammed.
ESD – ELECTROSTATIC DISCHARGE – The discharge of static electricity, which has built up on an insulative
material.
FIELD SERVICE M O DE – A PCM mode of operation that is used during service. It is operational when the engine is
running and the DLC diagnostic "test" enable terminal is grounded.
FUSE – A thin metal strip that melts when excessive current flows through it, thereby stopping current flow and
protecting a circuit from damage.
HC – HYDROCARBONS – One of the pollutants found in engine exhaust.
HIGH – A voltage more than a specific threshold such as ground or zero.
HYSTERESIS - Movement that does not follow the same path as it entered an area as it exits.
IAC – IDLE AIR CONTROL VALVE – Installed in the throttle body unit and controlled by the PCM to regulate idle air
flow, and thus idle RPM.
IAT – INT AKE AIR TEMPERATURE SENSOR – Senses intake manifold incoming air temperature, and passes that
information to the PCM.
IDEAL – The air/f uel ratio that provides the best perform ance, while maintaining m aximum conversion of exhaust
emissions, typically 14.7 to 1 on petrol engines.
IGN – IGNITION
INPUTS – Information from sensors (MAF, TPS, etc.) and switches (A/C request, etc.) used by the PCM to
determine how to control it's outputs.
INTERMITTENT – Occur s now and then; not continuously. In electrical circuits , refers to occasional open, shor t, or
ground.
I.C. – INSTRUMENT CLUSTER
LOW – A voltage less than a specific threshold. Operates the same as a ground and may, or may not, be
connected to chassis ground.
MAF – MASS AIR FLOW SENSOR – A device that m onitors the amount of air flow flowing into the engine intake.
The MAF sensor sends a signal to the PCM.
MIL – MALFUNCTION INDICATOR LAMP – Warning indicator with the outline of an engine. The "check powertrain
lamp " is located on the instrum ent panel, and is contr olled by the PCM. The MIL is illum inated by the PCM when it
detects a malfunction in the engine or transmission management system. The MIL is on when the ignition is "ON"
with the engine not running (bulb check).
MODE – A particular state of operation.
N.C. - NORMALLY CLOSED – Switch contacts that are connected, or together, when no outside forces
(temperature, pressure, position) are applied.
N.O. – NORMALLY OPEN – Switch contacts that are not connected, or not together, when no outside forces
(temperature, pressure, position) are applied.
NOx – NITROGEN OXIDES – One of the pollutants found in engine exhaust.
O2 - OXYGEN
OXYGEN SENSOR – Exhaust gas oxygen sensor, fitted in the exhaust manifold. Senses leftover oxygen after the
combustion process, and produces a very small electrical signal based on the amount of oxygen in the exhaust gas,
as compared to oxygen in the atmosphere.
OPEN LOOP – Describes PCM control of the fuel control system without use of oxygen sensor information.
OUTPUT – Functions, typically solenoids and relays that are controlled by the PCM.
PCM – POWERTRAIN CONTROL MODULE – A metal cased box (located in passenger com partm ent) containing
electronic circuitry that electrically monitors and controls the transmission system and emission systems of the
engine management system. It also turns "ON" the MIL when a malfunction occurs in the system.
PCV – POSITIVE CRANKCASE VENTILAT ION – Method of re-burning crankcase fumes, rather than passing them
directly into the atmosphere.
PFI – PORT FUEL INJECT ION – Method of injec ting fuel into the engine. Plac es a fuel inj ector at each inlet port of
a cylinder head, directly in front of the intake valve, mounted in the intake manifold.
PROM – PROGRAMMABLE READ ONLY MEMORY – an electronic term used to describe the engine calibration
unit. A plug-in memory unit that instructs the PCM how to operate for a particular vehicle.
PWM – PULSE WIDTH MODULATED – A digital signal turned "ON" and "OFF'" for a percentage of available on-
plus-off cycle time, such as 30% "on" and 70% "off" would be called a 30% "ON" PWM signal.
QUAD DRIVER – A "chip" device in the PCM, capable of operating four separate outputs. Outputs can be either
"ON-OFF" or pulse width modulated.
RAM – RANDOM ACCESS MEMORY – Is the microprocessors "scratch pad". The processor can write into, or
read fr om this m em ory as needed. This m em ory is volatile and needs a constant s upply of voltage to be retained. If
the voltage is lost or removed, this memory is lost.
SERIAL DATA – Serial data is a series of rapidly changing voltage signals pulsed from high to low voltage. These
voltage signals are typically 5 volts (high) and 0 volts (low) and are transmitted through a wire often referred to as
the serial data line.
SEQUENTIAL FUEL INJECTION – A mode of injecting fuel into the engine on the intake stroke of each cylinder.
SOLENOID – An electromagnetic coil that creates a magnetic field when current flows through it and causes a
plunger or ball to move.
SUPPRESSION CAPACITORS – These capacitors are connected between the power and ground circuits of the
cooling fan motors. These capacitors are for controlling fan motor noise in the radio.
SWITCH – Opens and closes circuits, thereby stopping or allowing current flow.
TCC – TORQUE CONVERTER CLUTCH – PCM controlled solenoid in automatic transmissions that, when
switched on, positively couples the transmission input shaft to the engine.
TECH 2 SCAN TOOL – A hand-held diagnostic tool, c ontaining a micropr ocessor to interpret the PCM's DLC data
stream. A display panel displays the PCM input signals and output commands.
TP SENSOR - THROTTLE POSITION SENSOR – A device that tells the PCM the current throttle position, and,
when it is moving, the rate of throttle opening / closing.
VACUUM, MANIFOLD – Vacuum source in the engine.
VACUUM , PORTED – Vacuum s our ced from a small "por t" in the throttle body. With the throttle closed, there would
be no vacuum meas ured, because the port is on the air cleaner side of the throttle blade, and is expos ed to engine
vacuum only after the throttle is open.
VSS - VEHICLE SPEED SENSOR (Vehicles with Automatic Transmission) – A per manent m agnet type sensor
which produces AC voltage which is sent to the PCM to determine vehicle speed.
UART - UNIVERSAL ASYNCHRONOUS RECEIVE AND TRANSMIT - A method of communicating between two
electronic devices.
WOT – WIDE OPEN THROTTLE – The throttle valve in the throttle body is at maximum opening.