SECTION 6C1-2 - DIAGNOSIS V6 ENGINE
IMPORTANT:
Before performing any Service Operation or other procedure described in this Section, refer to Section 00
CAUTIONS AND NOTES in VX Service Information for correct workshop practices with regards to safety
and/or property damage.
GENERAL DESCRIPTI O N
This is where to start all driveability and emissions diagnosis, once you read and understand
Section 6C1-1 GENERAL INFORMATION of the VX Series Service Information. The beginning of
Section 6C1-2A contains reference material: wiring diagrams, control module terminal end views, and engine
component locations. Remember, this information is for reference; do not start diagnosis using these pages.
Always start diagnosis on the page titled Powertrain OBD System Check. This check verifies that the diagnostic
circuits are operating properly, then sends you to the correct service manual page for diagnosis.
If the initial steps in the Powertrain OBD System Check reveal a problem, or if the engine does not s tart, you will be
using one or more tables in Section 6C1-2A of the VX Series Service Information for diagnosis. The Powertrain
OBD System Check will s end you to the correc t table. These tables f ollow the Powertr ain OBD System Check and
problems that prevent the engine from starting.
If the Powertrain OBD System Check shows that diagnostic trouble codes have been stored, proceed to the
appropriate Diagnostic Trouble Code (DTC) diagnosis pages. If more than one diagnostic trouble code has been
stored, always start diagnostic trouble code diagnosis with the lowest diagnostic trouble code number and work
upward. Diagnostic trouble code diagnosis pages start immediately after the diagnosis tables in Section 6C1-2A.
DIAGNOSTIC PRECAUTIONS
THE FOLLOWING REQUIREMENTS MUST BE OBSERVED WHEN WORKING ON VEHICLES.
1. Before removing any PCM system component, disconnect the battery earth lead.
2. Never start the engine without the battery being solidly connected.
3. Never separate the battery from the on board electrical system while the engine is running.
4. When charging the battery, disconnect the battery from the vehicle's electrical system.
5. Never subject the PCM to temperatures above 80° C i.e. paint oven. Always remove control unit first if this
temperature is to be exceeded.
6. Ensure that all cable harness plugs are connected solidly and that battery terminals are thoroughly clean.
7. The powertrain m anagem ent s ystem harnes s connec tors ar e designed to fit in only one way; there are indexing
tabs and slots on both halves of the connector. Forcing the connector into place is not necessary if it is being
installed with the proper orientation. Failure to take care to match the indexing tabs and slots to ensure the
connector is being installed correctly can cause damage to the connector, the module, or other vehicle
components or systems.
8. Never connect or disconnect the cable harness plug at the PCM when the ignition is switched ON.
9. Before attempting any electric Arc welding on the vehicle, disconnect the battery leads and the PCM
connectors.
10. When steam cleaning engines, do not direct the steam cleaning nozzle at PCM system components. If this
happens, corrosion of the terminals can take place.
11. Use only the test equipment specified in the diagnostic tables, since other test equipment may either give
incorrect results or damage good components.
12. All voltage m easurements using a voltmeter must use a digital m ultimeter with an internal im pedance rating of
at least 10 million ohms per volt (10 mega ohms) such as the DMM J 39200.
13. When a test light is specified, a "low-power" test light must be used. Do not use a high - wattage test light.
W hile a particular brand of test light is not suggested, a simple test on any test light will ensure it to be OK f or
PCM circuit testing. Connect an accurate ammeter (such as the high-impedance digital multimeter) in series
with the test light being tested, and power the test light-ammeter circuit with the vehicle battery.
Figure 6C1-2-1
If the ammeter indicates less than 3/10 amp current flow (0.3 A or 300 ma), the test light is OK to use.
If the ammeter indicates more than 3/10 amp current flow (0.3 A or 300 ma), the test light is NOT OK to use.
+
BATTERY
-
DC AMPS
Test Li
g
ht
BLOCKING DRIVE WHEELS
The vehicle drive wheels always should be blocked and the parking brake firmly set while checking any system.
VISUAL/PHYSICAL INSPECTION
A car ef ul vis ual and physical ins pection mus t be performed as par t of any diagnostic procedur e. T his c an of ten lead
to fixing a problem without further steps. Inspect all the wires in the engine compartment for bad connections,
burned or chafed spots, pinched wires, or contact with sharp edges or hot exhaust manifolds. Also, inspect all the
wires. Check beneath the air cleaner, the compressor, the generator, etc. This visual/physical inspection is very
important. The inspection must be done carefully and thoroughly.
BASIC KNOW LE DGE AND TOOLS REQUIRED
To use this service manual most effectively, a general understanding of basic electrical circuits and circuit testing
tools is required. You should be familiar with wiring diagrams, the meaning of voltage, ohms, amps, the basic
theories of electricity, and understand what happens in an open or shorted circuit.
To perform system diagnosis, the following tools are required.
• A Tech 2
• A test light
• A digital multimeter with 10 megaohms impedance
• A vacuum gauge
• A fuel pressure gauge and suitable fittings
• Fuel injector coil/ balance tester
• IAC motor analyser
Familiarise yourself with the tools and their uses before attempting diagnosis. Special tools that are required for
system service and the ones described above are illustrated in Section 6 SPECIAL TOOLS, at the end of this
Section.
ELECTROSTATIC DISCHARGE DAMAGE
Electronic components used to control the systems are often designed to carry very low voltage. They are very
susc eptible to damage caus ed by electros tatic discharge. It is pos sible for less than 100 volts of static electr icity to
cause damage to some electronic components.
By comparison, it takes as much as 4,000 volts for a person to even feel the zap of a static discharge.
There are several ways for a person to become statically charged. The m ost comm on m ethods of charging are by
fric tion and by induction. An ex ample of charging by friction is a per son sliding acr oss a car seat, in which a charge
of as much as 25,000 volts can build.
Charging by induction occurs when a person with well-insulated shoes stands near a highly charged object and
momentarily touches earth. Charges of the same polarity are drained off, leaving the person highly charged with
the opposite polarity. Static charges of either type can cause damage, therefore, use care when handling and
testing the electronic components.
NOTE: To prevent possible Electrostatic Discharge damage:
Do Not touch the PCM connector pins or soldered components on the PCM circuit board.
DIAGNOSTIC INFORMATION
The diagnostic tables and functional checks in this manual are designed to locate a faulty circuit or component
through logic based on the process of elimination. The tables are prepared with the understanding that the vehicle:
• Functioned correctly at the time of assembly.
• There are no multiple faults.
• The problem currently exists.
The PCM per form s a continual s elf- diagnosis on c ertain contr ol func tions. T his diagnos tic capability is supported by
the diagnostic procedures. The PCM indicates the source of a fault through the use of Diagnostic Trouble Codes
(DTCs). The DTCs are four digit (PCM will be P0XXX or P1XXX). When a fault is detected by the PCM, a
diagnostic trouble code will set and the Check Powertrain Malfunction Indicator Lamp (MIL) lamp may illuminate.
SELF-DIAGNOSTICS
The PCM performs system self diagnostics. The PCM can detect and often isolate system faults. W hen a fault is
detected, the PCM sets a DT C that represents the ar ea of the fault. The PCM m ay or may not turn ON the "Check
Powertrain" Lamp.
CHECK POWERTRAIN MALFUNCTION INDICATOR LAMP (MIL)
The instruments receive Check Powertrain MIL
information from the PCM via the serial data bus
normal mode message.
The PCM will command the instruments to turn on
the Check Powertrain MIL for two seconds when
the ignition is first turned on and when a DTC has
been set and the DTC requires the lamp to be
illuminated.
If the instruments do not receive a normal mode
mes sage from the PCM, the MIL will be illuminated
continuously. When the Check Powertrain MIL
remains ON while the engine is running, or when a
fault is s uspected due to a driveability or emiss ions
problem, perform the "On-Board Diagnostic
System Check". Refer to POWERTRAIN OBD
SYSTEM CHECK in Section 6C1-2A of the VX
Series Service Information. These checks will help
identify faults which may not be detected if other
diagnostics are performed.
Figure 6C3-2-2 Check Powertrain Malfunction
Indicator Lamp
INTERMITTENT CHECK POWERTRAIN MALFUNCTION INDICATOR LAMP (MIL)
In the case of an "intermittent" problem, the Check Powertrain MIL may light for ten seconds and then go out.
The corresponding Diagnostic Trouble Code will be stored. The DT C will remain stored until the battery voltage
to the PCM has been disconnec ted or until it is eras ed using the Tec h 2 scan tool. When unexpected diagnos tic
trouble codes appear, chances are that these diagnostic trouble codes were set by an intermittent fault.
An intermittent DTC m ay not re-set. If an intermittent fault occurs, do not use a Diagnostic Trouble Code Table.
Consult the "Diagnostic Aids " on the facing page. T he diagnostic table cor responds to the interm ittent diagnostic
trouble code.
Section 6C1-2B - SYMPTOMS TABLES of the VX Series Service Information also covers the topic of
"Interm ittents." A physical inspection of the applic able sub-system mos t often will resolve the problem . The Tech
2 scan tool also has several features which can help in diagnosing intermittent problems.
Figure 6C3-2-3 Check Powertrain Lamp Circuit
DATA LINK CONNECTOR (DLC)
The DLC is a standardised 16 way connector
located below the instruments panel and close to
the steering column.
1
3
2
Figure 6C3-2-4 Data Link Connector (DLC) Location
1. Steering Column Lower Cover
2. Data Link Connector
3. Instrument Panel Right Hand Cover Assembly
M
I
C
R
O
VXPCM30
INSTRUMENTPCM
12 SERIAL
DATA
5V
G/W (1220)
LOC. E3
R/B (1221)
CHECK
POWERTRAIN
LAMP
12V
5V
5V
D9
C13
SERIAL
DATA
DIAGNOSTIC
ENABLE
W/B (451)
BCM
E2
D2 E9
D3
DATA LINK
CONNECTOR
1546
1613129
B (150)
B/Y (155 )
M
I
C
R
O
YE111
YE112
YB198
YE111
YE114
YB66
YB164
YB175
YB164
YB175
YB128
The DLC pin 1 is the Secondary UART serial data
circuit.
Tech 2 does not communicate with anything on
terminal 1 this is only used for engineering
purposes.
Pin 4 is the earth circuit for Tech 2, Pin 5 is an
auxiliary earth, that should be used to earth the
Diagnostic Test Enable Circuits.
The DLC pin 6 is the PCM Diagnostic Test Enable
circuit. T his circ uit when jumper ed to DLC pin 5 will
cause the PCM enter the Diagnostic Mode. The
PCM Diagnostic Mode is described later.
The DLC pin 9 is the primary UART serial data
circuit. The Tech 2 scan tool uses this circuit to
read serial data information from the PCM and
BCM, Instruments, Electronic Climate Control, and
the ABS/ETC Control Modules.
The DLC pin 12 is the ABS/ETC Diagnostic Test
Enable circuit. This circuit when jumpered to DLC
pin 5 will cause the ABS/ETC Control Module to
enter the Diagnostic Mode and flash out ABS/ECT
trouble codes.
The DLC is designed to provide battery voltage to
pin 16 from fuse F31. This circuit is used to power
the Tech 2 scan tool.
1
9
2
10
3
11
4
12
5
13
6
14
7
15
8
16
Figure 6C3-2-5 Data Link Connector (DLC)
1. Secondary Serial Data (UART)
4. Earth
5. Earth
6. Diagnostic Test Enable
9. Primary Serial Data (UART)
12. ABS Diagnostic Test Enable
16. Battery Voltage
Figure 6C3-2-6 Data Link Connector Circuits
VXPCM057
PCM
C13 SERIAL
DATA
MAIN
5V
LOC. E3
BCM
E2/D2
E9/D3
E3/D13
M
I
C
R
O
SERIAL
DATA
MAIN
SERIAL
DATA AUX.
5V
G/W (1220)
W/G (1220)
HIGH SERIES
BCM TERMINALS
NOMINATED FIRST
DATA
LINK
CONNECTOR
1
2345678
9 10111213141516
5V
D9
DIAGNOSTIC
ENABLE
W/B (451)
B/Y (155)
B (150)
R/B (1221)
INSTRUMENTS
ABS/ETC
11
SERIAL
DATA
5V
12
17
SERIAL
DATA
5V
M
I
C
R
O
CHECK
POWERTRAIN
LAMP
OIL PRESSU RE
WARNING LAMP
POWER
ECONOMY LAMP
R
12V
P
N
D
3
1
2
SRS
ECC
9
6
M
I
C
R
O
M
I
C
R
O
SERIAL
DATA
SERIAL
DATA
5V
12V IGN
VEHICLE
SPEED
SPEEDOMETER
VEHICLE SPEED
C1
V/W (123)
M
I
C
R
O
M
I
C
R
O
P
R
O
C
E
S
S
O
R
YE114
YB175
YB164
YE111 YB198
YE112
YB190
YB87
YE98
YE110
YB66
YB128
YE114
STRATEGY BASED DIAGNOSTICS
The s tr ategy based diagnos tic is a uniform approac h to repair all Elec tric al/Elec tr onic ( E/E) s ystem s . T he diagnos tic
flow can always be used to resolve an E/E s ystem problem and is a star ting point when repairs are necess ary. The
steps below are def ined to instruct the technician how to proceed with a diagnostic. Steps below also ref er to step
numbers found on the Strategy Based Diagnostic table.
1. Verify the Customer Concern: To verify the customer concern, the technician should know the normal
operation of the system.
2. Preliminary Check: Conduct a through visual and operational inspection, review the service history, detect
unusual sounds or odours, and gather diagnostic trouble code information to achieve effective repair.
3. Service information (Manual) System Check(s): System checks verify proper operation of the system. This
will lead the technician in an organised approach to diagnostics.
4. Check Bulletins an d Other Service Info rmation: This should include videos, newsletters, and ser vice centre
updates.
5. Service Diagnostics (Paper/Electronic)
5.1 DTC Stored: Follow the designed DTC table exactly to make an effective repair.
5.2 Symptom, No DTC: Select the symptom from the symptom tables and follow the diagnostic paths or
suggestions to complete the repair, or refer to the applicable component/system checks in Section 6C1-2C.
5.3 No Published Diagnostics: Analyze the complaint and develop a plan for diagnostics. Utilise the wiring
diagrams and theory of operation.
Call technical assistance for similar cases where repair history may be available. Combine technician
knowledge with efficient use of the available service information.
5.4 Intermittent: Conditions that are not always present are intermittent. To resolve intermittents, perform the
following steps:
5.4.1 Observe history DTCs, DTC modes.
5.4.2 Evaluate the symptoms and conditions described by the customer.
5.4.3 Use a check sheet or other method to identify the circuit or electrical system component.
5.4.4 Follow the suggestions for intermittent diagnosis found in the service documentation.
The Tech 2 and DMM have data capturing capabilities that can assist in detection of intermittents.
5.5 Vehicle Operates As Designed/No Trouble Found: This condition exist when the vehicle is found to
operating norm ally. The condition desc ribed by the custom er m ay be nor mal. Verif y agains t another vehicle that
is operating normally. The condition may be intermittent. Contact Technical Assistance if the concern is
common. Verify the complaint under the conditions described by the customer before releasing the vehicle.
6. Re-examine the Concern: When the complaint cannot be successfully found or isolated, a reevaluation is
necessary. The complaint should be re-verified and could be intermittent or normal as per step 5.3 or 5.5.
7. Repair and Verificat ion Tests: After isolating the cause, the r epair should be m ade. Then validate f or proper
operation and verify that the symptom has been corrected. This may involve road testing or other m ethods to
verify the complaint has been resolved under the following conditions:
• Conditions noted by the customer.
• If a DTC was diagnosed, verify a repair by duplicating conditions for setting the DTC.
Figure 6C1-2-7 Strategy Based Diagnostic Table
STRATEGY BASED DIAGNOSTICS
VERIFY CUSTOMER CONCERN
PRELIMI NARY CHECKS
Visual and Operational
Perform Published
POWERTRAI N OBD SYSTEM CHECK
CHECK FOR BULLETINS
(Printed/DCS/Techline Equipment)
1
2
3
4
STORED SYMPTOM
DTC(S) NO DTC(S)
FOLLOW FOLLOW
PUBLISHED PUBLISHED
DTC SYMPTOM
DIAGNOSTICS DIAGNOSTICS
NO PUBLISHED INTERMITTENT
DIA GNOSTICS
Analyze & Develop SEE
Diagnostics or Call DIAG NO STIC
Technical DETAILS
Assistance
5.1 5.2 5.3 5.4
OPERATING AS DESIGNED
• Customer Misunderstanding of System:
Refer to Management or Zone
• Product Problem: Call Technical
Assistance
ISOLATE THE PROBLEM
REPAIR & VERI FY FIX
RE-EXA MINE
THE CONCERN
5.5
NO
Y
ES
7
6
CURRENT DIAGNOSTIC TROUBLE CODES
A current diagnostic trouble code is one that is set in the vehicle at this time. The current diagnostic trouble code
can be flashed out on the "Check Powertrain" lam p by earthing the data link connector term inal "6". The diagnostic
trouble code can also be displayed on the Tech 2 scan tool by pressing the appropriate button at the appropriate
menu. W hen the diagnostic trouble code is displayed, a code descriptor will also be listed on the Tech 2 scan tool
screen. Use of the proper diagnostic trouble code Table will find the cause of the problem.
HISTORY DIAGNOSTIC TROUBLE CODE
A histor y Diagnostic T rouble Code ( DTC ) is one that was a curr ent trouble code at s om e point previously, however,
the fault that caused the diagnostic trouble code to be logged is no longer present. The way to identify whether a
DTC is current or history is to look at the DTC history information parameter "IGN CYCLES" the number is 0 the
DTC is cur rent, any other num ber m eans it's a history DTC. The his tory diagnos tic trouble code can be f lashed out
on the "Check Powertrain" lamp by earthing the data link connector terminal "6". The diagnostic trouble code can
also be displayed on the Tech 2 scan tool by pressing the proper button at the appropriate menu. Use of the
diagnostic trouble code Tables to find the cause of the problem for the history diagnostic trouble code may lead to
replacem ent of good com ponents. Whenever a history code is set Refer to Section 6C1-2B "Symptoms" and also
look at the "Diagnostic Aids" listed on the diagnostic trouble codes facing page for criteria to set the DTC. History
diagnostic trouble codes are usually caused by intermittent conditions.
HOW DTC HISTORY WORKS
When a DTC is set, up to eleven (11) parameters will always be stored with it. The first four (4) parameters are:
1 "Engine speed" - RPM when DTC set .
2. "Times from start" - how long the engine had been running when the DTC set.
3. Times occurred, - number (#) of DTC occurrences.
4. "Ignition cycles" - since DTC last appeared.
Depending upon the DTC, up to 7 additional param eters that are related to this specific DTCs are also stored, for
example, if DTC P0123 TP sensor circuit high voltage were set, the variable parameters would be: TPS signal,
mass air flow, battery voltage, reference voltage and RH LTFT.
HOW TO USE DTC HISTORY CODE INFORMATION
Based upon this information that is stored in DTC history information, the technician can obtain the DTC criteria
when the DTC set and should be able to get the DTC to become current again by repeating the criteria.
READING DTC'S
The provision for communicating with the PCM is the Data Link Connector (DLC). It is attached to the instrument
panel lower right hand trim, directly beneath the steering column. It is used in the assembly plant to receive
information in checking that the engine and transmission are operating properly before they leave the plant. The
diagnostic trouble c ode(s) stor ed in the PCM's m emory can be read either through a T ech 2 sc an tool, (a handheld
diagnostic scanner plugged into the DLC), or by counting the number of flashes of the (MIL) "Check Powertrain"
lamp when the diagnostic "test" term inal of the DLC is earthed. The DLC terminal "6" (diagnostic "test" terminal) is
the sixth terminal from the right of the DLC top row. The diagnostic "test" terminal is most easily earthed by
connecting it to term inal "5" (internal PCM earth). The ter minal "5" is to the lef t of term inal "6" on the top row of the
DLC.
Once terminals "5" and "6" have been connected, the ignition switch m ust be moved to the "ON" position, with the
engine not running. At this point, the (MIL) "Check Powertrain" lamp should flash Diagnostic Trouble Code 0012
consecutively as long as no other DTCs ar e stored in the PCMs m em ory. If there are any other DTCs stored in the
PCMs m emory, DTC 0012 will not flash, only the stored DTCs will be f lashed. T he P in front of every Engine DTC
indicates Powertrain, s o there is no need and impos sible to flas h a P so f or f lashing preposs ess the P is ignor ed. In
order to flash the 0 in the DTC, each 0 in the code number will flash the MIL ten (10) times. Then the following
number will f lash in proper sequence. F or DT C 0012 this would look like “ fir st num ber 0 ten f lashes, paus e, sec ond
number 0 ten flashes, pause, third number 1 one flash, pause, fourth number 2 two flashs, long pause. Then the
process would start over again. This would indicate code 0012 has flashed. Diagnostic Trouble Code 0012
indicates that there ar e no referenc e pulses com ing to the PCM and that the PCM's diagnostic system is operating.
If Diagnostic Trouble Code 0012 is not indicated and there are no other PCM stored DTCs, a
problem is present within the diagnostic system itself, and should be addressed by consulting the
"On Board Diagnostic (OBD) System Check" Table in this Section. All DTCs starting with P0101 will flash in
proper sequence.
CLEARING DTCS
To c lear the curr ent diagnostic tr ouble code f rom the m em ory of the PCM, either to determ ine if the m alfunc tion will
occur again or because repair has been completed, the PCM power feed must be disconnected for at least thirty
(30) seconds. The PCM power feed can be disconnected by turning the ignition "OFF" and disconnecting the
positive battery terminal. The Tech 2 scan tool has a special mode that must be used to clear both history and
current diagnostic trouble codes.
NOTE: To prevent PCM damage, the ignition must be "OFF" when disconnecting or reconnecting PCM power.
CLEARING DTC HISTORY
The Tech 2 scan tool is the only tool capable of clearing the DTC history. Disconnecting the battery or removing
fuse F31 will not erase DTC history, the Tech 2 scan tool sends a special message into the PCM to erase this
memory.
IGNITION CYCLE DEFAULT
If the ignition is cycled ("OFF" and "ON") 50 times without a particular fault reappearing, that DTC will be erased
from PCM memory and the ignition cycle counter in the PCM will be reset to zero.
PCM SLEEP TEST
After the ignition switch is turned "OFF," the PCM will continue to operate for several seconds. During this shut
down, the PCM will return the IAC back to a pos ition to be used on the next startup, de-energizing all the solenoids
and relays, then the PCM will "go to sleep". The PCM can be checked for this sleep test by monitoring the voltage
of DLC terminal "6" it should go from 5 volts to 0 volts. The Tech 2 scan tool will display updated data until the
sleep m ode is activated then the PCM will no longer send out serial data and the T ech 2 sc an tool will display DLC
DATA LOST.
DIAGNOSTIC MODE
W hen the diagnostic "test" term inal is earthed with the ignition "ON" and the engine stopped, the system will enter
what is called the Diagnostic Mode. In this mode the PCM will:
1. Display a Diagnostic Trouble Code 0012 by flashing the (MIL) "Check Powertrain" lam p (indicating the system
is operating correctly). Only if there are no other stored codes in the PCMs memory.
2. Display any stored diagnostic trouble codes by flashing the (MIL) "Check Powertrain" lamp. Each code will be
flashed one at a time until all codes have been flashed, then the code flashing process starts over again.
FIELD SERVICE MODE
If the diagnostic "test" terminal is earthed with the engine running, the system will enter the Field Service mode.
While the system is in Field Service Mode, new DTCs cannot be stored in the PCM.
PCM LEARNING ABILITY
The PCM has a "learning" ability which allows it to make corrections for minor variations in the engine or
transmission system to improve driveability.
TRANSMISSION ADAPT FUNCTION
The HYDRA-MATIC 4L60-E uses a feedback line pressure control system which has the ability to adapt the
system's line pressure to compensate for normal wear of clutch fiber plates, seals, springs, etc. This "learning"
feature is similar to what is used for engine fuel control, short term fuel correction, long term fuel trim.
The HYDRA-MATIC 4L60-E transmission only uses the adapt function for the 1-2 upshift. The PCM monitors
engine speed to determ ine if the shif t is occur ring too fast ( harsh) or too s low (soft) and adjus t the pressur e control
solenoid to maintain the correct shift feel. The line pressure can adapt to values ranging f rom 35 kPa below, to 70
kPa above normal line pressure.
If the battery is disconnected, to c lear diagnostic trouble codes or for other repair , the "learning" proc ess res ets and
begins again. A change m ay be noted in the vehicle's perform ance. T o "teach" the vehicle, res et the IAC valve and
ensure that the engine is at operating temperature. The vehicle should be driven at part throttle, with moderate
acceleration and idle conditions until normal performance returns.
TABLE A V6 PCM
ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK
STEP ACTION VALUE YES NO
1.
1. Ignition "ON" engine "STOPPED".
2. Observe the " CHECK POWERTRAIN" lamp (MIL).
Is the "CHECK POWERTRA IN" lamp (MIL) "ON" steady?
Go to Step 2 If
No, "CHECK
POWERTRAIN"
lamp, Go to
Table A-1 of the
VX Series
Service
Information
----------------------
If "CHECK
POWERTRAIN"
lamp is flashing
DTC 0012, Go to
Step 10
2. Jumper Data Link Connector (DLC) terminal "6" To "5".
Does "CHECK POWERTRAIN" lamp flash DTC 12? Go to Step 3 Go to Table A-1
of the VX Series
Service
Information
3. 1. Disconnect Data Link Connector jumper.
2. Install scan tool to Data Link Connector.
Does scan tool display PCM serial data.?
Go to Step 4 Go to Table A-2
of the VX Series
Service
Information
4. 1. Ignition "ON".
2. Using Tech 2 scan tool, check for DTC .
Is DTC P1255 set?
Go to DTC
P1255 Table Go to Step 5
5. Does engine crank? Go to Step 6 Go to
Table A-4.0
6. 1. With Tech 2 scan tool, display DTC(s).
Are any Diagnostic Trouble Codes displayed?
NOTE: Check both Current and History codes.
Refer To
Applicable DTC
Table.
Start with lowest
DTC
Go to Step 7
7. Does engine start? Go to Step 8 Go to
Table A-3.1
8. 1. Ignition "ON", engine "STOPPED".
2. Compare Tech 2 scan tool data with typical
values shown on scan data page.
Are values normal or within typical ranges?
Go to Step 9 Refer to indicated
"Component(s)-
System" checks
of the VX Series
Service
Information.
9. 1. Run engine until normal operating temperature is
reached.
2. Run engine at 1500 revolutions per minute for 2
minutes, then idle engine.
3. Compare Tech 2 scan data with typical values
shown on "scan data" page.
Are values normal or within typical ranges?
Refer to
"Symptom"
Diagnosis
Tables" in
Section 6C1-2B
of the VX Series
Service
Information
Refer to indicated
"Component(s)-
System "checks
of the VX Series
Service
Information
10. Check for earthed diagnostic "TEST" terminal circuit.
Was a problem found? Verify Repair Go to Step 11
11. Replace PCM.
Refer to Section 6C1-3 Service Operations of the VX
Series Service Information, for PCM Programming and
Security Link procedure.
Is action complete?
Verify Repair
Figure 6C1-2-8 Example of On-Board Diagnostic System Check
POWERTRAIN OBD SYSTEM CHECK
After the visual and physical underhood inspection, the Powertrain OBD System Check is the starting point for all
diagnostic procedures or finding the cause of an emissions test failure.
All diagnostic procedures must always begin with the Powertrain OBD System Check.
Diagnostic procedures must begin with the Powertrain OBD System Check, which represents an organised
approach for identifying system problems.
The POW ERTRAIN OBD SYSTEM CHECK mak es an initial check of the system, then will direct the technician to
other tables in this Section. It must be used as a starting point for all procedures. The entire Section is set up in a
specif ic order , that is, the POWERTRAIN O BD SYSTEM CHECK will lead the technician to other tables, and those
tables may lead to still other tables. THE SEQUENCE MUST BE FOLLOWED. The engine/transmission control
system uses many input signals and controls many output functions. If the correct diagnostic sequence is not
followed, incorrect diagnosis and replacement of serviceable parts may happen.
Diagnostic tables incorporate diagnos is proc edures us ing a T ech 2 sc an tool where possible. T his T ech 2 s can tool
is a sm all hand-held com puter in itself. Its job is to give information to a technician about what is happening in the
powertrain management system.
The Data Link Connector (DLC) is used by the assem bly plant to perform end of line tes ts. T his c onnector c an also
be used by technician to monitor certain inputs and output as seen by the electronic control module. The Tech 2
scan tool reads and displays the information (serial data) supplied to the data link connector from the Powertrain
Control Module (PCM).
The correct procedure to diagnose a problem is to follow three basic steps.
1. Are the On-Board Diagnostics working?: This is determined by performing the Powertrain OBD System
Check. Since this is the starting point for the diagnostic procedures or finding the cause of a failure, always
begin here.
If the On-Board Diagnostic s ar en't work ing, the Powertrain O BD System Check will lead to a diagnostic table to
correct the problem. If the On-Board Diagnostics are working correctly, the next step is:
2. Is there a Diagnostic Trouble Code stored?: If a diagnostic trouble code is stored, go directly to the
numbered diagnostic trouble code table. This will determine if the fault is still present. If no diagnostic trouble
code is stored, then:
3. Observe Serial Data transmitted by the PCM: This involves reading the information available on the Serial
Data Stream with a Tech 2 scan tool. Information on this tool and the m eaning of the various displays can be
found in the suc ceeding paragraphs. T ypical data readings under a particular operating condition c an be f ound
on the "Tech 2 Scan tool Data" page.
DLC TECH 2 SCAN TOOL
The PCM can communicate a variety of information through DLC connector. This data is transmitted at a high
frequency which requires a Tech 2 scan tool for interpretation.
TECH 2 SCAN TOOL EXPLANATION
To ex plain how the T ech 2 scan tool work s, let's think for a minute about how a television works . A television is an
electronic device that receives and processes information, and sends out information in a form that can be
understood by the person watching it. The television receives a signal (from a transmitting station) that is not
usable to the person.
The television processes it, then sends the signal to a screen. The person can then see the information that the
television transmitting station sent out. The Tech 2 scan tool is like the television because it also processes
information, sent to it by the PCM.
The information is sent out of the PCM to the Data Link Connector (DLC) serial data line. The Tech 2 scan tool
plugs into the data link connector, and the information is sent to the tool on its cable. The Tech 2 scan tool
processes the information, and "sends" the signal to a display screen on the tool.
Just like a television, you can select which "station" that you want to see. The difference is instead of seeing the
picture on a television, you "see" the display screen, and the "stations" that you can select on a Tech 2 scan tool
are the different input and output signals that are being processed by the PCM.
The Tech 2 scan tool has the ability to send messages back to the PCM to do different things such as switch
outputs "OFF " and "ON." This allows the technic ian to control the PCM. This c ontrol only lasts as long as the Tec h
2 scan tool is connected.
TECH 2 SCAN TOOL USES - POWERTRAIN CONTROL MODULE (PCM)
The T ech 2 scan tool is a us eful and quick way of comparing operating param eters of a poorly operating engine or
transmission with a known good one. For example, a sens or may shift its value but not s et a DT C. Comparis on with
a known good vehicle may uncover this problem.
The T ech 2 scan tool allows a quick check of sensors and switches which are inputs to the PCM. The PCM in the
vehicle sends out information to the Tech 2 scan tool at a very fast rate, and the display on the tool can update
quicker than a digital multimeter. The Tech 2 scan tool allows a technician to manipulate wiring harnesses or
components under the vehicle while observing the Tech 2 scan tool readout. This can help in locating intermittent
connections.
After you enter the proper vehicle information, the first display on the Tech 2 scan tool will ask for what type of
system to select from.
The following is a list of systems the Tech 2 will display:
F0: ENGINE
F1: TRANSMISSION
F3: CHASSIS
F4: BODY
After selecting F0: ENGINE, the scan tool will display:
V6
V8 GEN III
DTC CHECK
Other
Once the correct engine has been selected, the Tech 2 scan tool will now have seven test modes for diagnosis
and service of the PCM system. The six test modes are as follows:
• MODE F0: NORMAL MODE
In this mode, the scan tool will display various engine and transmission data and vehicle information.
The f ollowing PCM Norm al Mode controller usage table, indicates specific Control Modules using the PCM supplied
report status information:
PCM NORMAL MODE CONTROLLER USAGE TABLE
PCM NORMA L MODE
SCAN TOOL
PARAMETERS
USED BY:
Scan Tool S tring BCM INST ECC A BS/
ETC
Engine Speed √
√√
√
Coolant Tem perature √
√√
√ √
√√
√
Vehicl e S peed √
√√
√ √
√√
√
A/C Clutch
A/C Pressure √
√√
√
Low Speed Fan Request √
√√
√
Low Fan Run ON √
√√
√
Theft St atus √
√√
√
PCM DTC Status √
√√
√
Check P owertrain MIL √
√√
√
Fuel Used √
√√
√
Fuel Flow Rate √
√√
√
Engine Type √
√√
√
Transmission Coding
Fuel Type √
√√
√
Engine Oil Change √
√√
√
Transm i ssion Oil Change √
√√
√
Shift Pattern √
√√
√
Torque Multiplier √
√√
√
High Coolant Temperature
Oil Pressure Switch √
√√
√
PRNDL Switc h √
√√
√
Commanded Gear √
√√
√
PCM Chim e √
√√
√
• MODE F1: DIAGNOSTIC TROUBLE CODES
In this test mode, DTCs stored by the PCM maybe displayed or cleared. When entering this mode there are four
modes:
F0. Read Current DTC
F1. Read History DTC
F2: Clear Current DTC
F3: Clear History DTC
• MODE F2: DATA DISPLAY
In this test mode, the Tech 2 scan tool continuously monitors system data, such as: engine speed data, engine
coolant temperature etc. When entering this mode, there are three modes;
F0: All Data
Displays all engine input and output data.
F1: Inputs
Displays all input data to the PCM.
F2: Outputs
Displays all output data from the PCM.
• MODE F3: SNAPSHOT
In this test m ode, the Tec h 2 scan tool captur es data before and after a snapshot triggering condition which may or
may not set a DTC.
• MODE F4: MISC. TESTS
In this test mode, the Tech 2 scan tool performs software override commands of the PCM, to assist in problem
isolation during diagnostics.
F0: OUTPUT TESTS
F0: Fuel Pump
F1: A/C Clutch
F2: Check Powertrain Lamp
F3: High Fan
F4: Canister Purge
F5: Starter Relay
F1: IAC SYSTEM
F0: RPM Control: used to control engine RPM from 600 RPM to 1675 RPM.
F1: IAC Control: Used to control IAC steps from 0 to 255 in 25 step increments.
F2: IAC Reset: used to reset IAC if the IAC is lost or if IAC has been replaced.
F3: Base Idle: used to set the engine to base idle.
F2: EGR CONTROL
This test will allow for control of the EGR by increments of 10% to decrease or increase EGR flow up to 100% on
time.
F3: RESET CELLS
Resets all LT Fuel Trim values to 0%
F4: BYPASS SPARK
With the engine running, this command turns on the bypass control circuit.
F5: A/F RATIO
With the engine running, forces air fuel ratio from 11.7 to 17.7.
F6: LPG FCV TEST
This test will allow for control of the FCV by increments of 7% to decrease or increase FCV flow up to 100% on
time.
F7: LPG ENABLE TEST
Used to command the LPG enable circuit on and off.
• MODE F5: FUNCTIONS
The Functions Tests m ode perf orms func tional tests on the PCM system which help verif y proper operation. In this
mode, fault conditions are automatically logged by the Tech 2 scan tool.
The Tech 2 scan tool also has the ability to send commands to the PCM, instructing the PCM to perform various
functions or tasks. This provides a quick way to determine if a device is operational or not.
In the F5 mode, the following tests can be performed:
F0: IAC Circuit
Designed to confirm to IAC motor functions OK and is not losing track of position. Monitor the engine
speed. Repeatedly cycles the IAC motor in and out and then monitors the engine speed. If OK, then
ignition "OFF" and start repeatedly, then stabilize. If the value of final RPM - initial RPM is greater than a
calibrated threshold, then the IAC circuit has failed.
F1: O2 Sensor
Designed to confirm oxygen sensor is functioning OK and not biased or slow responding. Monitors oxygen
sensor voltages and cross counts when in "Closed Loop" and forces rich/lean "Open Loop" operation.
F2: Power Balance
Designed to identify low power output from individual cylinders. Automatically cycles each injector "OFF"
than "ON" while monitoring and recording the RPM drop for each cylinder.
F3: Wiring Harness
Designed to confirm no intermittent open or short circuits exit in selected circuits. Engine is at idle in "N".
Technician should wiggle powertrain harness. The Tech 2 scan tool monitors inputs that should remain
relatively static at idle such as: ECT, IAT, TP Sensor, VSS, CAM signal present, 18X signal present, EST
lines, injec tor voltage monitor, batter y, ignition. If disc ontinuity occurs , the T ech 2 scan tool logs f ailure and
prompts technician to check appropriate circuit.
F4: Low Fan
Designed to confirm that the PCM will send a command to the BCM to turn "ON" the low speed fan.
F5: LPG Setup
This is us ed to lock the vehicle in a f ixed s tate in or der f or the LPG fuel system mix ture adjus tment screw to
be adjusted. T he PCM will set the following to a pre determ ined s etting in order f or the adjus tm ent scr ew to
be adjusted:
• Fixed Spark
• IAC Fixed to 800 RPM
• Fixed FCV to 40%
• MODE F6: FIELD SERVICE
In this test mode, With the ignition "ON" and the engine stopped, the Tech 2 scan tool will earth the diagnostic
"test" terminal. The system will display a Diagnostic Trouble Code 0012 by flashing the (MIL) "Check Powertrain "
lamp (indicating the system is operating correctly).
MODE F7: STALL DATA
Designed to capture nine (9) particular data values, when the engine is in a stall condition. This is very similar to
DTC History mode. The PCM will store the first stall condition 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.
• MODE F8: SPECIAL FUNCTIONS
PCM SETUP
In this mode Tech 2 programs the PCMM with an identifier number. It is only possible to perform the PCM setup
procedure once TIS approval has been obtained from TIS 2000, during the setup procedure Tech 2 will write the
identifier number into the PCM memory.
This PCM setup will have to be perform ed anytime the PCM has been reprogram med or a service PCM has been
installed into the vehicle. If a service PCM is installed into a vehicle the setup procedure will begin automatically
the first time Tech 2 communicates with the PCM.
TECH 2 SCAN TOOL: STALL DATA
SCAN POSITION UNITS DISPLAYED
ENGINE SPEED RPM
TIME FROM START TIME
TIMES OCCURRED NUMBER
IGNIT I ON CYCLES NUMBER
IDEL AIR CONTROL STEPS
VEHICLE SPEED KM/H
BATTERY VOLTAGE VOLTS
THROTTLE ANGLE 0-100%
A/C REQUEST NO/YES
TECH 2 SCAN TOOL USE WITH INTERMITTENT FAULTS
The T ech 2 scan tool allows m anipulation of wiring harnesses or c omponents under the bonnet with the engine not
running, while observing the Tech 2 scan tool readout.
The Tech 2 scan tool can be plugged in and observed while driving the vehicle under the condition when the
"Check Powertrain" lam p turns ON m omentar ily or when the engine driveability is mom entarily poor . If the problem
seems to be related to certain parameters that can be checked on the Tech 2 scan tool, they should be checked
while driving the vehicle. If there does not seem to be any connection between the problem and any specific c ircuit,
the Tech 2 scan tool can be used to monitor each parameter, watching for a period of time to see if there is any
change in the readings that indicates intermittent condition.
The Tech 2 scan tool can capture and store data when the problem occurs, so it can be played back at a slower
rate to determine what happened to the system. This is called the "SNAPSHOT" mode.
The Tech 2 scan tool is an easy way to compare the operating par ameters of a poorly operating engine with those
of a known good one. For example, a sensor may shift in value but not set a DTC. Comparing the sensor's
readings with those of a known good vehicle may uncover the problem.
The Tech 2 s can tool s aves time in diagnosis and helps to prevent the r eplac ement of s er viceable par ts. The k ey to
using the Tech 2 scan tool successfully is the technician's ability to understand the system being diagnosed, as
well as understanding the Tech 2 scan tool operation and limitations. The technician should read the Tech 2
operator’s manual to become familiar with the Tech 2 scan tool operation.
With an understanding of the data which the tool displays, and knowledge of the circuits involved, the tool can be
very useful in obtaining information which would be more difficult or impossible to obtain with other equipment.
The T ech 2 scan tool does not make the use of diagnostic tables unnecessary, nor can it indicate exactly where a
problem is in a particular circuit. Diagnostic Tables inc orporate diagnosis pr ocedures that require the use of a T ech
2 scan tool.
TECH 2 SCAN TOOL LIMITATIONS
The Tec h 2 sc an tool m ust receive the s ignal f rom the PCM in or der to display any useable inf orm ation. If the PCM
sends no signals to the data link connec tor, or the connec tion to the Tech 2 sc an tool is defec tive, the Tech 2 scan
tool will only display, "WAITING FOR DATA - NO DATA RECEIVED FROM PCM." The Powertrain OBD System
Check instructs the technician what to do if this happens.
The T ech 2 sc an tool has a few lim itations. If the T ech 2 sc an tool is displaying a PCM "output" function, it displays
only the com mand given by the PCM. That does not m ean that the desired action took place. This is s imilar to the
automatic transmission dashboard gearshift indicator. Just because the gearshift P R N D L pointer indicates the
transm ission is in DRIVE does not mean that the trans mission is actually in that gear. T o be sure, you m ust check
the linkage and adjustment at the transmission.
When using the T ech 2 s c an tool to obs erve one of the PCM "output" functions, s uc h as an idle air c ontrol motor, or
a TCC s olenoid, the technician must not assume the indic ated is the same as the actual. If the Tech 2 scan tool is
displaying TCC solenoid as being "ON," but the wire to power it is disconnected or defective, the PCM in some
cases has no way of knowing it. The display may indicate the command is "ON," but the device may not be
operating!
The Tech 2 s can tool s aves time in diagnosis and helps to prevent the r eplac ement of s er viceable par ts. The k ey to
using the Tech 2 scan tool successfully for diagnosis is the technician's ability to understand the system being
diagnosed, as well as an understanding of the Tech 2 scan tool's limitations.
With an understanding of the data the Tec h 2 scan tool dis plays, and knowledge of the circuits involved, the T ech 2
scan tool is useful in obtaining information which is difficult or impossible to retrieve with other methods.
Remem ber, the Tech 2 scan tool does NOT make using diagnostic tables unnecessary, nor can it tell you exactly
where a problem is in a circuit. Most diagnostic tables incorporate diagnosis procedures that require the use of a
Tech 2 scan tool.
TECH 2 SCAN TOOL: PCM NORMAL MODE
The Tech 2 scan T ool Norm al Mode in the table m ay be used fo r comparis on if a status repor t is being sent from
the PCM.
1. After completing the Powertrain OBD System Check
2. Finding the on-board diagnostics are functioning properly and
3. No diagnostic DTCs are displayed.
A TECH 2 SCAN TOOL THAT DISPLAYS FAULTY DATA SHOULD NOT BE USED, AND THE PROBLEM
SHOULD BE REPORTED TO THE MANUFACTURER. THE USE OF A FAULTY TECH 2 SCAN TOOL CAN
RESULT IN MISDIAGNOSIS AND UNNECESSARY PARTS REPLACEMENT.
Only the parameters listed are used for diagnosis. For more description on the values and use of the Tech 2 scan
tool to diagnosis PCM inputs, refer to the applicable diagnosis table. If all values are within the range illustrated,
refer to Section 6C1-2B - SYMPTOMS of the VX Series Service Information.
Test Description: The number(s) below refer to the number(s) on the Tech 2 Scan Data Engine Stream table.
1. T he T ech 2 sc an tool FO: PCM N ORMAL MOD E will display s can positions that will be displayed in order. The
Tech 2 scan tool will display nine (9) scan position parameters at a time. The down arrow button will scroll
down through all of the scan positions one at a time. After TIME FROM START parameter is displayed,
pressing the down arrow button again, will display scan position parameters starting at the top of the list again.
2. UNITS DISPLAYED are the available ways of displaying what each parameter is currently operating in, or a
value that is being sensed or being issued by the PCM.
3. TYPICAL DATA VALUE is separated into two parts. These displayed values are typical of a normally
operating vehicle. The IGNITION ON comparison should be performed first as this may lead to a quick
identification of a failure. The ENGINE RUNNING data should be compared to the IGNITION ON data as a
diagnostic check to make sure the component or system is operating properly.
4. IGNITION ON values are the typical values that should be seen on the Tech 2 scan tool with the ignition ON
and engine stopped. Temperature sensors should be compared to the actual temperatures by allowing the
sensor to cool overnight and then comparing their values. A difference of 3-5° C from the actual temperature
may indicate a problem with the sensor. Use the diagnostic aids table for that sensor to compare the
resistance to temperature values.
5. ENGINE RUNNING typical data values are an average of display values recorded from normally operating
vehicles at normally operating temperature. They are intended to represent what a normally functioning
system would typically display.
TECH 2 SCAN TOOL: PCM NORMAL MODE
TYPICAL DATA VALUE S
SCAN POSITION Q UNITS DISPLAYED
R IGNITION ON T ENGINE RUNNING U
ENGINE SPEED RPM 0 RPM 600 - 650 RPM
(± 50 RPM IN DRIVE)
COOLANT TEMPERATURE DEGREES C Varies +96 C
VEHICLE SPEED km/h 0 0
A/C CLUTCH ON /OFF OFF OFF
A/C PRESSURE kPa 896 kPa 800 - 1000 kPa A/C OFF
1600 - 1900 kPa A/C ON
LOW SPEED FAN REQUEST ON / OFF OFF OFF
LOW FAN RUN ON YES / NO NO NO
THEFT STATUS NO START / START START START
PCM DTC STATUS NO DTC(s)/DTC(s)
SET NO DTC(s) NO DTC(s)
CHECK POWERTRAIN
MALFUNCTION INDICATOR
LAMP (MIL)
OFF/ON ON OFF
FUEL USED L 00.00 1 - 2 L/Hour
FUEL FLOW RATE 00.00 1 - 2 L/Hour
ENGINE TYPE V6, V8,
V6
SUPERCHARGE,
V8 GEN 3
V8 GEN 3 V8 GEN 3
TRANSMISSION CODING MANUAL TRANS.
AUTO TRANS. MANUAL TRANS.
AUTO TRANS. MANUAL TRANS.
AUTO TRANS.
FUEL TYPE PETROL / LPG PETROL PETROL
ENGINE OIL CHANGE OKAY /
SERVICE
REQUIRED
OKAY OKAY
TRANSMISSION OIL CHANGE OKAY /
SERVICE
REQUIRED
OKAY OKAY
SHIFT PATTERN POWER/ECONOMY ECONOMY ECONOMY
TORQUE MULTIPLIER
HIGH COOLANT
TEM PERATURE YES/NO NO NO
OIL PRESSURE SWITCH OFF/ON OFF OFF
PRNDL SWITCH INVALID /
P,R,N,D,3,2,1 INVALID
OR
GEAR SELECTED
INVALID
OR
GEAR SELECTED
COMMANDED GEAR P/N R, 1 P/N P/N
PCM CHIME YES/NO YES YES
TECH 2 SCAN TOOL: PCM NORMAL MODE DESCRIPTIONS
A list of explanations for each data message displayed on the Tech 2 scan tool is listed below. This information will
assist in diagnosing emission or driveability problems. The displays can be viewed while the vehicle is being driven.
Refer to “Powertrain OBD System Check” for additional information.
ENGINE SPEED: Tech 2 Displays a range of 0 to 9999 RPM
The engine speed is computed by the PCM f rom the fuel control reference input. It should remain close to desired
idle speed under various engine loads with engine idling.
COOLANT TEMPERATURE: Tech 2 Displays a range of -39°C to 140°C (-38°F to 284°F)
The Engine Coolant Temperature (ECT) sensor is mounted in the cylinder head of the left bank. The PCM apples
5.0 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as temperature
changes. W hen the sensor is cold (internal r esistance high), the PCM m onitors a high s ignal voltage and interprets
the voltage as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases
and the PCM interprets the lower voltage as a warm engine.
VEHICLE SPEED: Tech 2 Displays a range of 0 to 255 km/h
The vehicle speed sensor signal is converted into km/h and mph for display.
A/C CLUTCH: Tech 2 Displays "ON" or "OFF"
Represents the commanded state of the A/C clutch control relay. Clutch should be engaged when ON is displayed.
A/C PRESSURE: Tech 2 Displays a range of 0 to 3195 kPa
The kPa displayed indicates that the PCM is monitoring an A/C Refrigerant Pressure signal voltage which is too
high or too low to allow the A/C compressor clutch to engage.
LOW SPEED FAN REQUEST: Tech 2 Displays "ON" or "OFF
Indicates if the engine cooling fan low speed relay has been commanded ON or OFF.
LOW FAN RUN ON: Tech 2 Displays "NO" or "YES"
This indicates if the PCM is requesting the BCM to turn the Low Speed Fan ON at key OFF.
THEFT STATUS: Tech 2 Displays "NO START" or "START"
Indicates the status of the Theft Deterrent System.
PCM DTC STATUS: Tech 2 Displays "NO DTC(s)" or “DTC SET”
Indicates if a DTC is set. This does not indicate what DTC is set, just informs that DTC are or are not set.
CHECK POWERTRAIN MALFUNCTION INDICATOR LAMP (MIL): Tech 2 Displays "OFF" or "ON"
Indicated if the instrument panel Malfunction Indicator Lamp is ON or OFF.
FUEL USED: Tech 2 Displays a range of 0 to 1000 Litres
When the key is turned ON, and the engine is running, the PCM will calculate FUEL USED during each ignition
cycle.
FUEL FLOW RATE: Tech 2 Displays a range of 0 to 100 litres
Indicates fuel consumption per litres per hour.
ENGINE TYPE: Tech 2 Displays Engine Type
The Tech 2 uses this information for proper Tech 2 scan tool software.
TRANSMISSION CODING: Tech 2 Displays “MANUAL” or “AUTOMATIC”
The Tech 2 uses this information for proper Tech 2 scan tool software
FUEL TYPE: Tech 2 Displays “PETROL” or “LPG”
The scan tool will display what fuel type the PCM software is set up for.
ENGINE OIL CHANGE: The Tech 2 Displays “OKAY” or “SERVICE REQUESTED”
The scan tool will display the status of the engine oil change condition.
TRANSMISSION OIL CHANGE: The Tech 2 Displays “OKAY” or “SERVICE REQUESTED”
The scan tool will display the status of the transmission oil change condition.
SHIFT PATTERN: Tech 2 Displays “ECONOMY” or “POWER”
This display shows the state of the POWER/ECONOMY switch.
TORQUE MULTIPLIER: Tech 2 Displays a range of 0 to
The display shows a calculated value derived from the Transmission Slip and Commanded Gear values. The
calculated value is used by the ABS/ETC module.
HIGH COOLANT TEMPERATURE: Tech 2 Displays "NO" or "YES"
This is an indication to the PCM that the engine is running hot. LOW COOLANT LEVEL: Tech 2 Displays "NO"
or "YES"
This is an indication to the PCM that the coolant level is low, and the PCM will turn on the Low Coolant lamp.
* (Only with GEN III V8 Engine)
OIL PRESSURE SWITCH: Tech 2 Displays "OFF" or "ON"
This is an indication to the PCM if the oil pressure is high or low. If the oil pressure is low, the PCM will turn on a
Low Oil Warning Lamp.
PRNDL SWITCH: Tech 2 Displays “INVALID” or “P, R, N, D, 3, 2, 1”
This displays if the vehicle is not equipped with a PRNDL switch (INVALID), or if equipped, indicates what gear the
driver has selected.
COMMANDED GEAR: Tech 2 Displays “1, 2, 3, 4”
The gear that the PCM is c om m anding the transmiss ion to be in. In PARK, the Tec h 2 sc an tool will display "1", the
commanded state of the shift.
PCM CHIME: Tech 2 Displays "NO" or "YES"
This is a indication to the instrument panel allowing the instrument panel to chime if a problem or fault is detected.
TECH 2 SCAN TOOL: ENGINE DATA
The Tech 2 scan Data listed in the table may be used for comparison
1. After completing the Powertrain OBD System Check
2. Finding the on-board diagnostics are functioning properly and
3. No diagnostic DTCs are displayed.
A TECH 2 SCAN TOOL THAT DISPLAYS FAULTY DATA SHOULD NOT BE USED, AND THE PROBLEM
SHOULD BE REPORTED TO THE MANUFACTURER. THE USE OF A FAULTY TECH 2 SCAN TOOL CAN
RESULT IN MISDIAGNOSIS AND UNNECESSARY PARTS REPLACEMENT.
Only the parameters listed are used for diagnosis. For more description on the values and use of the Tech 2 scan
tool to diagnosis PCM inputs, refer to the applicable diagnosis table. If all values are within the range illustrated,
refer to Section 6C1-2B - SYMPTOMS of the VX Series Service Information.
Test Description: The number(s) below refer to the number(s) on the Tech 2 Scan Data Engine Stream table.
1. The Tech 2 scan tool F2: DATA LIST will display scan position's that will be displayed in order. The Tech 2
scan tool will display nine (9) scan position parameters at a time. The down arrow button will scroll down
through all of the s can positions one at a tim e. After TIME F ROM START parameter is displayed, press ing the
down arrow button again, will display scan position parameters starting at the top of the list again.
2. UNITS DISPLAYED are the available ways of displaying what each parameter is currently operating in, or a
value that is being sensed or being issued by the PCM.
3. TYPICAL DATA VALUE is separated into two parts. T hese displayed values are typic al of a norm ally operating
vehicle. The IG NITION ON comparis on should be perform ed first as this may lead to a quick identif ication of a
failure. The ENGINE RUNNING data should be compared to the IGNITION ON data as a diagnostic check to
make sure the component or system is operating properly.
4. IGNITION ON values are the typical values that should be seen on the Tech 2 scan tool with the ignition ON,
and engine stopped. Temperature sensors should be compared to the actual temperatures by letting the
sensor stabilise overnight and then comparing their values. A diff erence of 3-5° C from the actual temperature
may indicate a problem with the s ensor . Us e the diagnos tic aids table f or that sens or to compare the r es istanc e
to temperature values.
5. ENGINE RUNNING typical data values are an average of display values recorded from normally operating
vehicles at norm ally operating tem perature. They are intended to represent what a norm ally functioning system
would typically display.
TECH 2 SCAN TOOL: ENGINE DATA
TYPICAL DATA VALUE S
SCAN POSITION Q UNITS DISPLAYED
R IGNITION ON T ENGINE RUNNING U
ENGINE SPEED RPM 0 RPM ± 100 RPM FROM DESIRED RPM
(± 50 RPM IN DRIVE)
DESIRED IDLE SPEED RPM 0 RPM PCM IDLE COMMAND (VARIES WITH
TEM PERATURE)
ENG. COOLANT TEMP (ECT) VOLTS VARIES +96° C
COOLANT TEMPERATURE DEGREES C VARIES VARIES
IAT VOLTS VARIES VARIES
INTAKE AIR TEMPERATURE DEGREES C VARIES VARIES
MAF SENSOR FREQUENCY Hz 0 Hz 2200-2500 Hz
MASS AIR FLOW GRAM /SEC 0 g/s 5 –10 g/s
MASS AIR FLW/CYL Mg/S 0.0 Mg/S 140 to 150 Mg/S
TPS SIGNAL 0-100 % 0 % 0 %
THROTTLE ANGLE VOLTS 0.32 V 0.47 V
RH 02 SENSOR READY YES/NO NO YES
LH 02 SENSOR READY YES/NO NO YES
RH 02 SENSOR Mv 447 Mv 100-1000 Mv AND VARYING
LH 02 SENSOR Mv 447 Mv 100-1000 Mv AND VARYING
RH ST FUEL TRIM + 100% TO –100% +0% + 0% +10% TO –10%
LH ST FUEL TRIM + 100% TO –100% +0% + 0% +10% TO –10%
LT FUEL TRIM R + 100% to – 100 % + 0 % + 0 % + 10% to – 10%
LT FUEL TRIM L + 100% to – 100 % + 0 % + 0 % + 10% to – 10%
LTFT ENABLE YES / NO NO NO
FUELING MODE OPEN / CLOSED
LOOP OPEN LOOP CLOSED LOOP
LTFT CELL CELL # 0 0
RH O2 STATUS RICH / LEAN LEAN LEAN
LH O2 STATUS RICH / LEAN LEAN LEAN
RH O2 CROSS CNTS COUNTS 0 0
LH O2 CROSS CNTS COUNTS 0 0
STFT DELTA 0 – 100 % 0 % 0 %
LTFT DELTA 0 – 100 % 0 % 0 %
DECEL FUEL CUTOFF NO/YES NO NO
INJ. PULSE TIME Ms 27.5 Ms 3.25 Ms
INJECTOR VOLTAGE VOLTS 11.4 V 14.0 V
AIR / FUEL RATIO % 0.0 : 1 14.7 : 1
PURGE PWM % 0 % 10 %
EGR POS. COMMANDED % 0% 0%
EGR POS. FEEDBACK. % 0% 0%
EGR PINTLE SENSOR VOLTS VOLTS 0.6 VOLT 0.6 VOLT
BATTERY VOLTAGE VOLTS 11.3 V 14.0 V
REFERENCE VOLTS VOLTS 4.99 V 4.99 V
3X SIGNAL MISSING /
PRESENT MISSING PRESENT
18X SIGNAL MISSING /
PRESENT MISSING PRESENT
CAM SIGNAL MISSING
/PRESENT MISSING PRESENT
IAC POSITION STEPS 169 STEPS 22 STEPS
LITERS PER HOUR L/HR 00.00 1 - 2 L/Hour
IDLE RPM VARIANT. RPM 0 RPM 0 RPM
SPARK MODE BYPASS/EST BYPASS EST
SPARK ADVANCE DEGREES BTDC 14 ° BTDC + 14° BTDC
KNOCK SIGNAL CYLINDER 1 NONE/KOOCK
DETECTED NONE NONE
KNOCK SIGNAL CYLINDER 2 NONE/KOOCK
DETECTED NONE NONE
KNOCK SIGNAL CYLINDER 3 NONE/KOOCK
DETECTED NONE NONE
KNOCK SIGNAL CYLINDER 4 NONE/KOOCK
DETECTED NONE NONE
KNOCK SIGNAL CYLINDER 5 NONE/KOOCK
DETECTED NONE NONE
KNOCK SIGNAL CYLINDER 6 NONE/KOOCK
DETECTED NONE NONE
TECH 2 SCAN DATA ENGINE STREAM (CONTINUED)
TYPICAL DATA VALUE S
SCAN POSITION Q UNITS DISPLAYED
R IGNITION "ON" T ENGINE RUNNING U
KNOCK SIGNAL ANY
CYLINDER KNOCK/NONE NONE NONE
KNOCK RETARD # OF DEGREES 0 ° 0 °
KNOCK RETART CYLINDER 1 # OF DEGREES 0 ° 0 °
KNOCK RETART CYLINDER 2 # OF DEGREES 0 ° 0 °
KNOCK RETART CYLINDER 3 # OF DEGREES 0 ° 0 °
KNOCK RETART CYLINDER 4 # OF DEGREES 0 ° 0 °
KNOCK RETART CYLINDER 5 # OF DEGREES 0 ° 0 °
KNOCK RETART CYLINDER 6 # OF DEGREES 0 ° 0 °
TCC SOLENOID ON / OFF OFF OFF
VEHICLE SPEED KM / H 0 KM/H 0 KM/H
A/C REQUEST ON /OFF OFF OFF
A/C CLUTCH ON /OFF OFF OFF
A/C PRESS. VOLTS VOLTS 1 - 2 V 1 - 2 V
A/C PRESSURE SENSOR kPa 352 kPa 600 - 700 kPa A/C OFF
800 - 1000 kPa A/C ON
HIGH SPEED FAN ON / OFF OFF OFF
LOW SPEED FAN REQUEST ON / OFF OFF OFF
THEFT STATUS NO START/START START START
STARTER RELAY OFF/ON ON ON
FUEL PUMP RELAY ON / OFF OFF ON
CRANK TIME SEC 0.0 SEC 0.5 SEC
DTC STATUS NO DTC(s)/DTC(s)
SET NO DTC(s) NO DTC(s)
TIME FROM START TIME 0:00:00 VARIES
CHECK POWERTRAIN
MALFUNCTION INDICATOR
LAMP (MIL)
OFF/0N ON OFF
REQUESTED TORQUE N.m 214N.m 642N.m
(N.m WILL DECREASE WITH ENGINE
LOAD)
ACTUAL TORQUE N.m 0 N.m 35-45 N.m
( N.m WILL CLOSELY FOLLOW
REQUESTED TORQUE ONCE
ENGINE LOAD IS DETECTED)
LOW OIL PRESSURE NO/YES YES NO
LPG SWITCH OFF/ON OFF OFF
LPG FUEL ENABLE NO/YES NO NO
FUEL PETROL / LPG PETROL PETROL
LPG FUEL CONTROL VALVE 0-100 % 0% 0%
LPG MODE ENABLED NO/YES NO NO
LPG LOW PETROL CUTOUT NO/YES NO NO
LPG SMART SOLENOID
ENABLED NO/YES NO NO
TECH 2 SCAN TOOL: ENGINE DATA DESCRIPTIONS
A list of ex planations for each data m essage disp layed on the Tec h 2 scan tool begins as follows. This inf ormation
will assist in tracking down em ission or driveability problems, since the displays can be viewed while the vehicle is
being driven. Refer to the "On-Board Diagnostic System Check" for additional informational.
ENGINE SPEED - Range 0-9999 RPM - Engine speed is computed by the PCM from the fuel control reference
input. It should remain close to desired idle under various engine loads with engine idling.
DESIRED IDLE - Range 0-3175 RPM - T he idle s peed that is comm anded by the PCM. The PCM will com pensate
for various engine loads to keep the engine at the desired idle speed.
ECT SENSOR VOLTS/ENG COOLANT TEMP - Range -40 degrees to 151 degrees C/ 0 - 5 VOLTS - The
Engine Coolant Temperature (ECT) sensor is mounted in the inlet manifold and sends engine temperature
information to the PCM applies 5 volts to the coolant temperature sensor circuit. The sensor is a therm istor which
changes internal resistance as temperature changes. W hen the sensor is cold (internal resistance high), the PCM
monitors a high signal voltage which it interprets as a cold engine. As the sensor warms (internal resistance
decreases), the voltage signal will increase, the voltage signal will decrease and the PCM will interpret the lower
voltage as a warm engine.
IAT SENSOR VOLTS/IAT - Range -40 degrees to 151 degrees C - The PCM converts the resistance of the
intake air temperature sensor to degrees. Intake Air Temp (IAT) is used by the PCM to adjust fuel delivery and
spark timing according to incoming air density.
MAF SENSOR FREQUENCY - Range 0-10,192 Hz - T he signal that is sent from the Mass Air Flow ( MAF) sensor
to the PCM is in the for m of a frequency output. This f requency output changes as the dem and of engine air intake
changes.
MASS AIR FLOW - Range 0-246 Grams/Sec. - The Mass Air Flow (MAF) sensor measures the change in the
intake air flow which results from engine load and speed changes. As intake air flow increases, the air in the inlet
manifold also increases and addition fuel is required.
MASS AIR FLOW/CYL - Range 0-1000 mG/S. - Calculated air flow per each cylinder.
TPS SIGNAL - Range 0 to 5.10 Volts - Used by the PCM to determine the amount of throttle demanded by the
driver. Should read 0.25 - 1.25 volt at idle to above 4 volts at wide open throttle.
TPS ANGLE - Range 0-100% - Com puted by the PCM f rom T P sensor voltage (T hrottle position) should read 0%
at idle, 100% at Wide Open Throttle (WOT).
RH/LH OXYGEN SENSOR READY - Tech 2 Displays "YES" or "NO". Indicates if the 02 sensors have reached
operating temperature.
RH/LH OXYGEN SENSOR - Range 0-1192 - Represents the exhaust sensor output voltage. Should fluctuate
constantly within a range between 100 m V (Lean exhaust) and 1000 m V (Rich exhaust) when operating in "Closed
Loop".
ST FU EL T RIM R/L - Rang e -100% -0% -+ 100% - Short Term Fuel T r im repr esents a s hort- ter m corr ec tion to f uel
delivery by the PCM in response to the am ount of time the oxygen sensor voltage spends above or below the 450
mV thres hold. If the oxygen sensor voltage has m ainly been below 450 mV, indicating a lean air/f uel m ixtur e, STF T
will increase to tell the PCM to reduce fuel delivery to compensate for the indicated rich condition. Under certain
conditions suc h as ex tended idle and high ambient tem per atur es, c anis ter pur ge may cause STF T to r ead less than
-10%.
LT F UEL TRIM R/L -100% - 0% - +100% - LT FT is derived by the PCM from the ST FT value and is used f or long-
term correction of fuel delivery. A value of 0% indicates that fuel delivery requires no compensation to maintain a
14.7:1 air/fuel r atio. A value below 0% m eans that the fuel s ystem has been rich and f uel delivery is being r educed
(decreas ed injector pulse width) to m aintain a 14.7 to 1 A/F ratio. A value above 0% indicates that a lean condition
exists and the PCM has been compensating by adding fuel (increased injector pulse width). LTFT tends to follow
STFT, a value of less than -10% due to canister purge at idle should not be considered unusual.
LTFT ENABLE - Tech 2 Displays "Y ES" or "NO". - The Long T erm Fuel Trim is enable by the PCM when a long
term fuel correction is required. A YES indicates that the LTFT is enabled, a NO indicates that is not.
FUELING MODE - Tech 2 Displays "OPEN" or "CLOSED" - "Closed Loop" displayed indicates that the PCM is
controlling fuel delivery according to oxygen sensor voltage. In "Open Loop", the PCM ignores the oxygen sensor
voltage and bases the amount of fuel to be delivered on TP Sensor, coolant and IAT sensor inputs only. "Closed
Loop" operation should begin when the 02 sensor becomes active, engine coolant temperature exceeds 50
degrees C (122 degrees F) for more than 30 seconds and the PCM has seen a RPM of 1200 or greater for 10
seconds. At extremely high temperature or when towing a trailer, it is possible for the system to remain in "Open
Loop" operation to control catalytic converter temperatures.
LONG TERM FUEL TRIM CELL (LTFT CELL) - Range 0-34 - LTFT cell is dependent upon engine speed and
ma ss air f low readings and canister pur ge. A plot of RPM vs MAF is broken into 34 cells. LTFT cell indicates which
cell is currently active.
RH/LH 02 STATUS - Tech 2 Displays "RICH" or "LEAN" - Indicates whether exhaust oxygen sensor voltage is
above (rich) or below (lean) the 450 mV oxygen sensor threshold voltage. Should change constantly indicating that
the PCM is controlling the air/fuel mixture properly.
RH/LH O2 CROSS CNTS - Range 0-255 - The number of times the oxygen sensor voltage crosses over the
rich/lean threshold during a two second interval.
STFT /LT FT DELT A - Range 0-100%. - The dif fer ence (Delta) in % of the ST FT /LT FT counts f rom eac h bank. This
value is used by the PCM to determine bank to bank fuel trim balance.
DECEL FUEL CUTOFF - Tech 2 Displays "YES" or "NO" - Yes displayed indicates that the PCM has detected
conditions appropriate to operate in deceleration fuel mode. The PCM will command deceleration fuel mode when
a sudden decrease in throttle position has been detected while the vehicle is travelling over a certain KM/H. W hile
in deceleration fuel mode, the PCM will decrease the amount of fuel delivered by entering open loop and
decreasing the injector pulse width.
INJ. PULSE WIDTH TIME - Range 0.0 - 999.9 mS. - The "ON" time of the injector as determined by the PCM.
INJECTOR VOLTAGE - Range 0 - 14.0 Volts. System voltage monitoring
AIR/FUEL RATIO - Range 0.00 : 99.99 - The reading reflects the commanded value. This should be at or near
14.7. A lower number indicates a richer commanded air fuel mixture while a higher number indicates a leaner
mixture.
PURGE PWM - Range 0 - 100% - A propor tional signal used to control EVAP Canister Purge func tion. 0% im plies
the valve is commanded fully closed, while 100% implies that the value is fully open.
EGR POSITION COMMANDED - Range 0 - 100% - Represents the EGR pintle position that the PCM is
commanding. Desired EGR position should stay close to EGR Pintle Position.
EGR POSITION FEEDBACK - Range 0% - 100% - Represents the actual position of the EGR pintle in percent.
0% displayed indicates a fully extended pintle (EGR valve closed).
EGR PINTL E SENSOR - Range 0.0 - 5.0 Volts - Represents the voltage that the PCM us es to determ ine weather
or not the EGR valve is fully closed (0% pintle position).
BATTERY VOLTAGE - Range 0-25.5 volts - This represents the system voltage measured by the PCM at its
ignition No. 1 feed.
REFERENCE VOLTS - Range 0-5.10 Volts - Indicates the voltage that is supplied to various sensors from the
PCM.
3X SIGNAL - Range Missing or Present - Signal indicates crankshaft position for correct ignition coil sequencing.
18X SIGNAL - Range Missing or Present – Signal indicates the position of the crankshaft within the 3X cycle.
CAM SIGNAL - Range Missing or Present - Signal sent to the PCM by the Cam Sensor. This indicates
movement of the camshaft. This signal is used by the PCM to indicate if the engine is running.
IAC POSITION - Range 0-255 Counts - Displays the commanded position of the idle air control pintle in counts.
The higher the number of counts, the greater the commanded idle speed. Idle air control should respond fairly
quickly to changes in engine load to maintain desired idle RPM.
LITRES Per Hour - Range 0-100 - Indicates fuel consumption per litres per hour.
IDLE RPM VARIANT - Range 0-9999 RPM - Indicates the variation in RPM between sampling's of the engine
speed.
SPARK MODE - Tech 2 displays "BYPASS" or "EST" - Indicates what mode of ignition timing the vehicle is
operating under.
SPARK ADVANCE - Range -90 Degree to +90 Degree - T his is a display of the spark advance (EST ) calculation
which the PCM is program m ing into the ignition system. It com putes the desired spark advance using data such as
engine temperature, rpm, load, vehicle speed, and operating mode.
KNOCK SIGNAL CYLINDER (1 THROUGH 6) - Tech 2 Displays NONE or knock detected
- This signal indicates what cylinder is knocking.
KNOCK SIGNAL - Tech 2 Displays "KNOCK" or "NONE" - Indicates whether or not a knock signal is being
detected by the PCM. Should read "NONE" at idle.
KNOCK RET ARD - Rang e 0 Degrees - 90 Deg rees - Indic ates the amount of s par k advanc e the PCM is removing
from EST in response to the Knock sensor (ESC) signal. Should read 0 degrees at idle.
KNOCK RETARD CYLINDER (1 THROUG H 6) - Range 0 Degrees - 90 Degrees - Indicates the am ount of s park
advance the PCM is removing from each cylinder in response to the Knock sensor (ESC) signal. Should read 0
degrees at idle.
TCC SOLENOID - Tech 2 Displays "ON" or "OFF". - Indicates if the transmission TCC Solenoid is commanded
the TCC ON or OFF.
VEHICLE SPEED - Range 0-255 km/h - The vehicle speed sensor signal is converted into kph and mph for
display.
A/C REQU EST - T ech 2 Displays "YES" or "NO" - Repr esents the state of the A/C request serial data input f rom
the BCM.
A/C CLUTCH - Tech 2 Displays "ON" or "OFF" - Represents the commanded state of the A/C clutch control
relay. Clutch should be engaged when "ON" is displayed.
A/C PRESSURE - Tech 2 Displays 0.0 - 5.10 Volts - Represents the A/C r efrigerant press ure Sensor signal. The
amount of pressure indicates the amount of load that the A/C compressor is placing on the engine.
The PCM uses this information to adjust idle speed and to control the cooling fan.
A/C PRESSURE - Range 0 - 3195 kPa - The kPa displayed indicates that the PCM is monitoring an A/C
Refrigerant Pressure signal voltage which is too high or too low to allow the A/C compressor clutch to engage.
HIGH SPEED FAN - Tech 2 Displays "ON" or "OFF - Indicates if the engine cooling fan high speed relay has
been commanded ON or OFF.
LOW SPEED FAN REQUEST - Tech 2 Displays "ON" or "OFF - Indicates if the engine cooling fan low speed
relay has been commanded ON or OFF.
THEFT STATUS - Tech 2 Displays "NO START" or "START". - Indicates the status of the Theft Deterrent
System.
STARTER RELAY - T ech 2 Displays "OFF" or "ON" - If the scan tool indic ates ON, then the vehic le will start. As
long as the Theft Deterrent System is working properly, the scan tool should indicate "ON"
FUEL PUMP RELAY - Tech 2 Displays "ON" or "OFF. - Indicates if the Fuel Pump is ON or OFF.
CRANK TIME - Range 0 - 99.9 Seconds. - Indicates the duration of the engine crank time.
DTC ST ATUS - Tech 2 Displays "NO DTC(s)" or DT C SET - Indicates if a DTC is set. This does not indicate what
DTC is set, just informs that DTC are or are not set.
TIM E FROM START - Tech 2 Displays 0:00:00. - Indicates the hours, m inutes and seconds the engine has been
running.
CHECK POWERT RAIN MALFUNCT ION INDICAT OR LAM P (M IL) - Tech 2 Displays "OFF" or "ON" - Indicated
if the instrument panel Malfunction Indicator Lamp is "ON", or "OFF".
REQUESTED TORQUE - Tech 2 Displays 0 - 215 N.m of Torque - Indicates what N.m torque signal the
ABS/ETC module is sending to the PCM.
ACTUAL TORQUE - Tech 2 Displays 0 - 215 N.m Of Torque - Indicates the PCM N.m torque response back to
the ABS/ETC module.
LOW OIL PRESSURE - Tech 2 Displays "NO" or "YES" - Indicated if the PCM is detecting a low oil pressure
signal.
LPG SWITCH - Tech 2 Displays "OFF" or "ON" - Indicates which mode the driver has selected, Petrol or LPG
mode.
LPG FUEL ENABLE - Tech 2 Displays "NO" or "YES" Indicates if the PCM is capable of operating in LPG
mode..
FUEL - Tech 2 Displays Petrol or LPG - Indicates what type of fuelling mode the Vehicle is currently operating
under.
LPG FUEL CONTROL VALVE – Range 0% - 100% Represents the actual position of the FCV in percent. 0%
displayed indicates the FCV is OFF. 100% indicated the FCV is fully ON.
LPG MODE ENABLE – Tech 2 Displays "NO" or "YES" This indicates if the LPG mode has been selected.
TECH 2 SCAN TRANSMISSION DATA
The Tech 2 scan Data listed in the table may be used for comparison
1. After completing the "On-Board Diagnostic System Check"
2. Finding the on-board diagnostics are functioning properly and
3. No diagnostic DTCs are displayed.
A TECH 2 SCAN TOOL THAT DISPLAYS FAULTY DATA SHOULD NOT BE USED, AND THE PROBLEM
SHOULD BE REPORTED TO THE MANUFACTURER. THE USE OF A FAULTY TECH 2 SCAN TOOL CAN
RESULT IN MISDIAGNOSIS AND UNNECESSARY PARTS REPLACEMENT.
Only the parameters listed are us ed in this m anual f or diagnosis . For m or e descr iption on the values and use of the
Tec h 2 scan tool to diagnosis PCM inputs, r efer to the applicable diagnosis Table. If all values are within the range
illustrated, refer to Section 6C1-2B - SYMPTOMS of the VX Series Service Information.
Test Description: Number(s) below refer to circled number(s) on the Tech 2 scan tool Transmission Date Stream.
1. The Tech 2 scan tool "FO: DATA LIST " will display scan position's that w ill be displayed in order. The T ech 2
can tool will display nine (9) scan position parameters at a tim e. The "DOW N ARROW " button will scroll down
through all of the scan positions one at a time. After "CHECK POWERTRAIN MALFUNCTION INDICATOR
LAMP (MIL)" parameter is displayed, pressing the "DOWN ARROW" button again, will display scan position
parameters starting at the top of the list again.
2. "Units Dis played" are the available ways of displaying what each par ameter is c urrently operating in, or a value
that is being sensed or being outputted by the PCM.
3. "Typical Data Value" is separated into two parts. These displayed values are typical of a normally operating
vehicle. The ignition "ON" comparison should be performed first as this may lead to a quick identification of a
failure. The engine running data should be compared to the ignition "ON" data as a diagnostic check to m ake
sure the component or system is operating properly.
4. Ignition "ON" values are the typical values that should be seen on the Tech 2 scan tool with the ignition "ON,"
and engine stopped. Temperature sensors should be compared to the actual temperatures by letting the
sensor sit overnight and then comparing their values. A difference of 3-5 degrees C from the actual
temper ature may indicate a problem with the sens or. Use the diagnostic aids T able for that sensor to com pare
the resistance to temperature values.
Some "O N" or "OFF " switches may display an abnormal s tate. If the Table states this position is abnor mal, than
this may be caused by an open or short to earth, depending upon the normal state of the switch. Refer to the
proper Section or more information on diagnosis.
5. "ENGINE RUNNING" typical data values are an average of display values recorded from normally operating
vehicles at normal operating temperature, and are intended to represent what a normally functioning system
would typically display.
TECH 2 SCAN DATA TRANSMISSION STREA M
TYPICAL DATA VALUE S
SCAN POSITION Q UNITS DISPLAYED R IGNITION "ON" T ENGINE RUNNING U
ENGINE SPEED RPM 0 RPM ± 100 RPM FROM DESIRED RPM
(± 50 RPM IN DRIVE)
VEHICLE SPEED KM/H 0 0
TPS SIGNAL VOLTS 0.25V - 1.25V 0.25V - 1.25V
TPS ANGLE % 0% 0%
ECT SENSOR VOLTS VOLTS 1.9 V
(VARIES) 1.96 V
(VARIES)
ENG COOLANT TEMP 0C +960C
(VARIES) +960C
(VARIES)
TFT SENSOR VOLTS VOLTS 2.8 V
(VARIES) 2.8 V
(VARIES)
TFT 0C 940C
(VARIES) 940C
(VARIES)
TFP SWITCH A 0V - 12V 12 V 12 V
TFP SWITCH B 0V -12 V 0 V 0 V
TFP SWITCH C 0V - 12V 12 V 12 V
TFP GEAR P/N R,D, 3, 2,1 P/N P/N
PRNDL SWITCH INVALID /
P,R,N,D,3,2,1 INVALID
OR
GEAR SELECTED
INVALID
OR
GEAR SELECTED
TRANSMISSION RANGE (TR) PARK/NEUTRAL
REVERSE, Drive 4,
O/D, Drive 3, Drive 2,
Drive 1
PARK/NEUTRAL PARK/NEUTRAL
TR SWITCH P OPEN 12 V/CLOSED
0V CLOSED 0V CLOSED 0V
TR SWITCH A OPEN 12 V/CLOSED
0V CLOSED 0V OPEN 12V
TR SWITCH B OPEN 12 V/CLOSED
0V CLOSED 0V OPEN 12V
TR SWITCH C OPEN 12 V/CLOSED
0V CLOSED 0V CLOSED 0V
1 - 2 SHIFT SOLENOID ON/OFF OFF ON
2 - 3 SHIFT SOLENOID ON/OFF ON ON
1 - 2 SHIFT SOL. FDBK ON/OFF OFF ON
2 - 3 SHIFT SOL. FDBK ON/OFF ON OFF
1 - 2 SHIFT TIME SEC 0.00 0.00
2 - 3 SHIFT TIME SEC 0.00 0.00
COMMANDED. PCS MILLAMPS 0 MA 900 to 1000 MA
ACTUAL PCS MILLAMPS 0 MA 900 to 1000 MA
PCS DUTY CYCLE % 0 % 55 to 65 %
TCC SOLENOID ON/OFF OFF OFF
TCC PWM SOLENOID % 0% 0%
TRANS SLIP SPEED RPM 0 +700 to 800 RPM
SHIFT PATTERN ECONOMY, POWER,
CRUISE ECONOMY ECONOMY
3 - 2 DOWNSHIFT ENABLE YES/NO NO NO
3 - 2 DOWNSHIFT SOL. OFF/ON ON ON
LT 1 - 2 SHIFT. ADAPT kPa 0 kPa 0 kPa
LT 2 - 3 SHIFT. ADAPT kPa 0 kPa 0 kPa
SHORT TERM SHIFT ADAPT kPa - 32 kPa - 30 to -40 kPa
ADAPT SHIFT STATUS DISABLED/ENABLED ENABLED ENABLED
SHIFT ADAPT CELL 0 0 0
GEAR RATIO RATIO% 3.06:1 3.06:1
COMMANDED GEAR 1234 1 GEAR 1 GEAR
BATTERY VOLTAGE VOLTS 12.6 V 13.5 - 14.5V
TIME FROM START TIME 0:00:00 VARIES
CHECK POWERTRAIN
MALFUNCTION INDICATOR
LAMP (MIL)
OFF/0N ON OFF
TECH 2 SCAN TOOL: TRANSMISSION DATA DISPLAY DESCRIPTIONS
A list of ex planations for each data m essage disp layed on the Tec h 2 scan tool begins as follows. This inf ormation
will assist in tracking down em ission or driveability problems, since the displays can be viewed while the vehicle is
being driven. Refer to the "On-Board Diagnostic System Check" for additional informational.
ENGINE SPEED - Range 0-9999 RPM - Displays the PCM's interpretation of actual engine speed, as received
from the reference input signal. Displays in increments of 1 RPM. Often useful to detect if extra reference pulses
are suspected. A sudden high RPM indication while at a steady throttle would indicate electrical interference in the
reference input signal circuit. This interference is usually caused by PCM wires too close to ignition secondary
wires or an open reference earth circuit.
VEHICLE SPEED - Range 0-255 KM /H - Displays the PCM's interpretation of vehicle speed as received from the
PCM. If this position indicates no vehicle speed (zero), but the speedometer shows otherwise, then a Diagnostic
Trouble Code 24 will eventually set. Also useful for checking speedometer accuracy.
TPS VO LTAGE - Range 0-5.10 VO LTS - This position shows the T hrottle Position sensor signal input to the PCM.
Values read will be in voltage and will interpret the throttle opening to the PCM. T he voltage should between 0.25 -
1.25 volts with the throttle closed and go up to approximately 4.5 volts at Wide Open Throttle (WOT).
TPS ANGLE - Range 0-100% - This display is the PCM's interpretation of the percentage of throttle opening. TPS
angle should display zero (0%) with the throttle closed and 100% at Wide Open Throttle (WOT).
ECT SENSOR VOLTS/ENG COOLANT TEMP - Range -40 degrees to 151 degrees C/ 0 - 5.10 Volts - The
Engine Coolant Temperature (ECT) sensor is mounted in the inlet manifold and sends engine temperature
inform ation to the PCM applies 5 volts to the coolant tem per ature sens or circ uit. T he sensor circ uit. The sensor is a
therm istor which c hanges inter nal r esistanc e as tem perature c hanges. When the s ensor is c old (internal r esistance
high), the PCM monitors a high signal voltage which it interprets as a cold engine. As the sensor warms (internal
resistance decreases), the voltage signal will increase, the voltage signal will decrease and the PCM will interpret
the lower voltage as a warm engine.
TFT SENSOR VOLTS/TRANS FLUID TEMP - Range -40 degrees C to 151 degrees C/ 0 - 5.10 VOLTS - This
position will display the PCM's interpretation of temperature in the transmission. The Transmission Fluid
Tem per ature (T FT ) sens or is mounted in the valve body and is wired to the PCM. The PCM m onitor s the differenc e
in voltage between two terminals, and the T ECH 1 sc an tool will display TFT in voltage and a tem peratur e shown in
degrees Celsius. The TFT sensor reading should read close to the air temperature when the transmission is cold,
and increases as the transmission fluid temperature increases. After the engine is started the temperature should
rise steadily to about 82 degrees C- 94 degrees C then stabilise.
TFP SWITCH A/B/C VOLTS - Range 0 Volts or 12 VOLTS - These values represent the three fluid pressure
switch ass em bly signals. These lines are norm ally high and are taken low as the f luid pressure switch interprets the
manual valve position. The sequence of these signals is decoded by the PCM to determine the appropriate gear
range. O volts indicates closed, and 12 volts indicates open.
TFP GEAR - Tech 2 Displays P/N-R,D,3,2,1 - This value represents the decoded sequence of the Transmission
Fluid Pressure Manual Valve Position Switch Assembly (TFP). The TFP is used to determine the manual valve
position. The manual valve position is an input to the PCM used to control line pressure, TCC, and shift solenoid
operation.
PRNDL SWITCH - T ech 2 Displays Invalid or P, R, N, D, 3, 2, 1 - This dis plays if the vehicle is not equipped with
a PRNDL switch ( Invaded), or if equipped, indicates what gear the driver has selected.
TRANSMISSION RANGE (TR) - Tech 2 Displays PARK / NEUTRAL, REVERSE, PARK/NEUTRAL, DRIVE 4
O/D, DRIVE 3/D, DRIVE 2, DRIVE 1. T he scan tool dis plays the dec oded position of the trans miss ion Park/Neutr al
range switch (PRNDL). This information is then sent to the instrument panel and is displayed to the operator.
TR SWITCH A (TRANSMISSION RANGE) - Tech 2 Displays OPEN 12 V/CLOSED 0 V. This parameter is the
input from the automatic transmission Park/Neutral range switch. OPEN represents a B+ voltage signal and
CLOSED represents a 0 voltage signal.
TR SWITCH B (TRANSMISSION RANGE) - Tech 2 Displays OPEN 12 V/CLOSED 0 V. This parameter is the
input from the automatic transmission PARK/NEUTRAL range switch. OPEN represents a B+ voltage signal and
CLOSED represents a 0 voltage signal.
TR SWITCH C (TRANSMISSION RANGE) - Tech 2 Displays OPEN 12 V/CLOSED 0 V. This parameter is the
input from the automatic transmission Park/Neutral range switch. OPEN represents a B+ voltage signal and
CLOSED represents a 0 voltage signal.
TR SWITCH P (TRANSMISSION RANGE) - Tech 2 Displays OPEN 12 V/CLOSED 0 V. This parameter is the
input from the automatic transmission PARK/NEUTRAL range switch. OPEN represents a B+ voltage signal and
CLOSED represents a 0 voltage signal.
1-2 SHIFT SOLENOID, 2- 3 SHIFT SOLENOID - T he 2 Disp lays "ON" or "OF F" - This dis plays the "ON" or "O FF "
state of the two shift solenoids. The shift solenoids are turned "OFF" or "ON" to change gears.
1-2 AND 2- 3 SHIFT SO LENOID FEEDBACK - The 2 Displays ON/OF F - T he 2 Displays "ON" or "OFF" - These
values represent the true electrical state of the solenoids. The PCM uses this information to set malfunction DTC's.
1-2 SHIFT TIME -Tech 2 Displays Time - This value represents the time taken to shift from first gear to second
gear. This information is only accurate if the shift was adaptable.
2-3 SHIFT TIM E - Tech 2 Displays Time - T his value r epresents the tim e taken to shift f rom s econd gear to third
gear. This information is only accurate if the shift was adaptable.
COM MANDED PCS - Tech 2 Range 0 t o 1000 Millamps - This value r epres ents the c omm anded pr es sur e c ontro l
solenoid current. The commanded current is determined from the manual valve position, transmission fluid
temperature, transmission output speed, shift solenoid state, TCC, A/C status, engine speed, TCC slip and the
throttle pos ition sensor . The com manded pressur e control solenoid cur rent is then used to c ontrol the transm ission
line pressure.
ACTUAL PCS - Tech 2 Range 0 to 1000 Millamps - This value represents the actual pressure control solenoid
current. This value should always be very similar to the desired pressure control solenoid current. If the actual
deviates from the desired by 0.16 amps, a DTC will set.
PCS DUTY CYCLE - The 2 Range 0 to 100 % - This value represents the pressure control solenoid duty cycle.
This value is determined by the desired pressure control solenoid current.
TCC SOLENOID - The 2 Displays "ON" or "OFF" - The Torque Converter Clutch (TCC) solenoid is an
electronically controlled exhaust valve. W hen energised (provided an earth) by the PCM, the TCC solenoid stops
converter signal fluid from exhausting. The closing of the solenoid valve causes converter signal fluid pressure to
increase and shift the converter clutch apply valve into the apply position.
This value represents the status of the Torque Converter Clutch (TCC) solenoid. This status is determined by
throttle position, transmission output speed, transmission range, engine coolant temperature, transmission fluid
temperature, and TCC slip.
TCC PWM SOLENOID - Tech 2 Displays 0 to 100 % - A proportional signal used to control TCC function 0%
implies that the TCC solenoid is commanded fully closed, while 100% implies that the TCC solenoid is fully open.
TRANS SLIP SPEED - Tech 2 Displays RPM - This displays the calculated difference between the engine RPM
and the transmission input shaft RPM. This TCC slip RPM should be +/- 30 to the actual engine RPM if TCC is
applied.
SHIFT PATTERN - Tech 2 Displays ECONOMY, POWER OR CURISE - This display shows the state of the
Economy /Power switch or the Cruise Switch.
3-2 DOWNSHIFT ENABLE - Tech 2 Displays "YES" or "NO" - This value represents the state of the 3-2
downshift contr ol solenoid. T his devic e regulates the re lease of the 3- 4 clutch and the apply of the 2-4 band. The 3-
2 solenoid is normally "NO", except during a 3-2 downshift when it switches to "YES". The solenoid will be NO in
first gear. The solenoid YES state is determined by throttle position, vehicle speed, and the commanded gear.
3-2 DOWNSHIFT SOL FDBK - T ech 2 Displays "OFF" or "ON" - T hese values repr esent the true electric al state
of the solenoid and circuit. The PCM uses this information to set a DTC.
LONG TERM 1 - 2 SHIFT ADAPT -
LONG TERM 2 - 3 SHIFT ADAPT -
SHORT TERM 1 - 2 SHIFT ADAPT
AD AP T S H I F T S T ATU S - T his value indicates if the cur rent s hift will update the 1-2 adapt tables which are us ed to
modify line pressure. The following are used to determine if the shift should be adapted.
Braking pressures (manual gear ranges).
Long shift delay is the time the solenoid changes state until the shift starts.
Long shift time.
Throttle range.
Changes of throttle.
Hot mode
Transmission fluid temperature range.
Manual gear ranges (1, 2).
If shift starts too soon after the solenoid state changes.
Diagnostic failure.
SHIF T ADAPT CE LL - This value displays the cell that the PCM is operating in. These are three cells available to
adapt the s hift, these cells are: Light throttle, Medium throttle and Full throttle. Thes e three cells are very similar to
LTFT cell used by the engine.
GEAR RATIO - This display represents the gear ratio of the commanded gear. 1st 3.06:1, 2nd 1.63:1, 3rd 1.00:1,
4th 0.69:1, Rev 2.29 :1.
COM M ANDED G EAR - T ech 2 Displays 1, 2,, 3, 4 - The gear that the PCM is c omm anding the tr ans mission to be
in. In Park, the Tech 2 scan tool will display "1", the commanded state of the shift.
BATTERY VOLTAGE - Range 0-25.5 VOLTS - This represents the system voltage measured by the PCM at its
ignition No. 1 feed.
TIM E FROM START - Tech 2 Displays 0:00:00 - Indicates the hours, m inutes and seconds the engine has been
running.
CHECK POWERT RAIN MALFUNCT ION INDICAT OR LAM P (M IL) - Tech 2 Displays "OFF" or "ON" - Indicated
if the instrument panel Malfunction Indicator Lamp is "ON", or "OFF".
TIM E FROM START - Tech 2 Displays 0:00:00 - Indicates the hours, m inutes and seconds the engine has been
running.
CHECK POWERT RAIN MALFUNCT ION INDICAT OR LAM P (M IL) - Tech 2 Displays "OFF" or "ON" - Indicated
if the instrument panel Malfunction Indicator Lamp is "ON", or "OFF".
DIAGNOSTIC TABLES
INTRODUCTION
The diagnostic tables are designed to provide fast and efficient means of fault location for all engine and
transmission functions associated with the PCM. Each diagnostic table uses 2 pages; a table on the right side
page, and a facing page on the left side page. The left side "facing page" contains pertinent information, including
diagnostic trouble code setting parameters and circuit diagrams. The table steps are explained by the
corresponding numbered paragraph on the left side facing page.
When diagnosing any problem, always begin with THE ON-BOARD DIAGNOSTIC SYSTEM CHECK The On-
Board Diagnos tic System Chec k will lead you to the other tables. DO NOT GO DIRECT LY TO A SPECIFIC T ABLE
or false diagnosis and replacement of serviceable parts could result.After a fault is corrected and all DTCs have
been cleared, repeat the On-Board Diagnostic System Check to assure that the proper repairs have been made.
The "A" Table pages and the diagnostic trouble code diagnostics pages are constructed in a similar fashion. The
box at the top of the left page contains a wiring diagram showing the components involved in each circuit.
Immediately below the box is a brief circuit description. On the facing right-hand page a troubleshooting table for
diagnosing c onditions. Step numbers on the right- hand page nex t to the action box es in the table relate to the items
in the Test Decription on the left-hand page. These items provide an explanation of each test in the table.
The appropriate step in any of the trouble shooting table will instruct you either to make a specific repair or to
continue diagnosis. If further diagnosis is needed, the step will specify where to continue.
The Yes or No column in any diagnostic table will instruct you either to make a specific repair or to continue
diagnosis. If further diagnosis is needed, the Yes or No column will specify where to continue.
If the condition is intermittent, the trouble shooting table will direct you to the diagnostic aids on the facing page.
This Section gives suggestions for diagnosing intermittent conditions and explains how some faults can occur.
Remember, tables are for solving active conditions or diagnostic trouble codes, not intermittent conditions. Use
symptom diagnosis for solving intermittent conditions.
4271
Figure 6C1-2-9 Diagnostic Flow Table Typical
WRITING THE REPAIR ORDER
The repair order is one of the most important tools
a technician can have. Like his other tools, the
repair order must be highly accurate to give him
the greatest help.
It's up to the service adviser to supply the
technician with this highly accurate tool. Problems
begin for the technician when the repair order is
incomplete or is incorrect.
An incomplete repair order doesn't provide the
technician with a good starting point for the
diagnosis. Consequently, the tec hnician may was te
time, using a “ shotgun” approach attem pting to find
the problem.
An incorrectly written repair order can lead the
technician down the wrong diagnostic path,
preventing him from finding the problem.
Consequently, a service adviser needs to write an
accurate and complete repair order. This is
accomplished by asking the customer these
questions: WHO? WHAT? WHEN? WHERE? and
HOW?
Figure 6C1-2-10 An Incomplete Repair Order
"WHO"? QUESTIONS
"WHO"? is the first question you need to ask. As
you begin to fill out the repair order, you need to
find out who was driving the vehicle when the
problem occurred and talk directly to that person if
at all possible.
This allows you to give first-hand information on
the problem to the technician, which is critical to
diagnosing the problem. If you can't talk directly to
this person, get their name and phone number so
the technician can call the customer if needed.
"WHAT"? QUESTIONS
The next step is to find out "WHAT"? the problem
is. If it's a driveability problem, and it seems to be
complex, bring the technician who's going to work
on the vehicle into the picture if at all possible.
Allow the technician to question the customer
directly, so he can get the information he needs to
help him diagnose the pr oblem . Again, this is s o he
can get first-hand knowledge of the problem.
If you don't involve the technician with the
customer, you need to ask if the "Check
Powertrain" lamp is ON all the time, coming ON
and OFF during the same key cycle, or is never
ON.
Figure 6C1-2-11 Typical Symptomatic Diagnostic Table
This is important to the technician because this
informs him which diagnostic direction to take.
These tables are different from one another. If a
technician is f ollowing the wrong table, a lot of time
is wasted. So, ask the customer questions about
the "Check Powertrain" lamp.
Other good "WHAT"? questions are. Under what
conditions did the problem occur?
Were they accelerating, decelerating, or coasting?
Were they driving in the city or on the freeway?
What were the environmental conditions? Was it
raining? snowing? hot? cold? The technician may
need to duplicate these conditions as closely as
possible if he is to find the cause of the problem.
"WHEN"? QUESTIONS
"WHEN"? questions are the next step. If the
customer says the "Check Powertrain" lamp was
ON, you need to ask when the Check Powertrain
came ON and how long it has been "ON." Is the
Check Powertrain ON before or during starting, or
when the engine is running?
More im portant, you need to ask when the problem
first oc curred. Maybe it began af ter the vehicle was
serviced f or a related pr oblem or for som ething that
appears to be totally unrelated.
The technician also needs to know if the problem
has become worse. This information may give the
technician som e clues as to what the problem may
be.
"WHERE"? QUESTIONS
"WHERE"? is the next question. The location
where the problem occurs may give the technician
an idea as to what may be contributing to the
problem, such as electromagnetic interference
from overhead power lines.
"HOW"? QUESTIONS
To round out your questioning, you need to ask the
customer "HOW"? often the problem occurs. This
can give the technician direction as to what type of
system may be causing the problem: electrical,
mechanical, vacuum, etc.
4273
Figure 6C1-2-12 Typical Diagnostic Table
SUMMARY
In summary , you need to obtain the following information from the customer:
• Who the principal driver is.
• What the problem is.
• When the problem began.
• Where the problem occurs.
• How often the problem occurs.
Complete answers to these questions will aid the technician in diagnosing the problem.
VERIFYING THE COMPLAINT
ENGINE COMPARTMENT INSPECTION
The most important step in diagnosing a driveability complaint is to verify the complaint. This means you have to
duplicate the problem if possible.
Start by performing an engine compartment inspection. Check the integrity of all the electrical connections and
vacuum hoses, etc. Also, check the wire routing for the possibility of Electromagnetic Interference (EMI).
CHECKING FOR STORED DIAGNOSTIC TROUBLE CODES
As you check for diagnostic trouble codes, keep in mind that intermittent faults may not store a diagnostic trouble
code. So proceed with verifying the complaint, even if no diagnostic trouble codes are stored.
If a diagnostic trouble code is stored, check the service bulletins for the particular vehicle you're working on.
ROAD TESTING THE VEHICLE
This step is optional if the repair order states.
• The driveability problem is intermittent.
• You did not find any problems under the bonnet .
• No diagnostic trouble codes are stored.
Then you need to road test the vehicle in order to recreate the problem.
This is an important step because the problem has to be present in order to repair the problem.
Most intermittent driveability problems are repeatable. That is what road testing is all about.
Before you go on your road test, review the vehicle's ser vice histor y. This information c an give you clues as to what
may be causing the driveability problem and what you need to watch.
Read the repair order and think about what systems could possibly cause the problem. This is essential to finding
the problem. Think about how the system or systems in question works, what inputs are needed and what could
cause the problem.
Check all the inputs required f or a circuit, whether the circuit actually has trouble or if you only suspect trouble. All
inputs are needed and m ust be within a "normal" r ange. You will want to pay attention to these system s and circuits
during and after the road test.
As you're road testing, put the Tech 2 scan tool in the snapshot mode so you can capture the system data when
the problem occurs.
Do not discount the other information the Tech 2 snapshot mode can supply you with.
DON'T FORGET THE BASICS
Whether or not you find anything wrong during the road test, don't forget the basics.
Electrical connections such as power feeds and earths are vital to the operation of almost all of the vehicle
systems.
No matter how good the system is, it is still working in combination with the engine. If the engine is not in good
condition, the computer system can't make up for the condition.
Compare performance problems, such as lack of power, with a comparable vehicle. This will let you know if the
customer complaint really is a problem or something that is normal.
If you can't repeat the problem, and you need more information for diagnosing, call the customer who was driving
the vehicle when the problem occurred. This type of professionalism will probably help you diagnose the problem.
CALIBRATIONS
If a vehicle is just starting to have an intermittent driveability problem and it has accumulated more than 30,000
kilometers, chances are that the PCM calibration is not at fault.
If the vehicle was r unning properly for such a long tim e, the original PCM calibrations are not the problem since the
PCM calibrations don't change, the chances of the calibrations going bad are rare. There may however be an
updated calibration for a particular condition, so check service bulletins for calibrations updates.