
ON-BOARD DIAGNOSTICS
TABLE OF CONTENTS
page
ON-BOARD DIAGNOSTICS
DESCRIPTION............................6
ON-BOARD DIAGNOSTICS
DESCRIPTION - DIAGNOSTIC TROUBLE CODES
On the following pages, a list of DTC's is provided
for the 2.5L diesel engine. A DTC indicates that the
ECM has recognized an abnormal signal in a circuit
or the system. A DTC may indicate the result of a
failure, but most likely will not identify the failed
component directly. Refer to the appropriate diagnos-
tic manual for more information on diagnosis of trou-
ble codes.
ACCESSING DIAGNOSTIC TROUBLE CODES
A stored DTC can be displayed through the use of
the DRB IIItscan tool. The DRB IIItconnects to the
data link connector. The data link connector is
located under the instrument panel near bottom of
the steering column (Fig. 1).
ERASING TROUBLE CODES
After the problem has been repaired, use the DRB
IIItscan tool to erase a DTC.
ENGINE CONTROL MODULE (ECM) - DRBIIITCODES
Generic Scan Tool Code DRB IIITScan Tool Display
P0070 Ambient Air Temperature Circuit Signal Voltage Too High
Ambient Air Temperature Circuit Signal Voltage Too Low
P0100 Mass Air Flow Sensor Plausibility
Mass Air Flow Sensor Plausibility Positive Area
Mass Air Flow Sensor Signal Voltage Too High
Mass Air Flow Sensor Signal Voltage Too Low
Mass Air Flow Sensor Supply Voltage Too High Or Low
P0105 Barometric Pressure Circuit Signal Voltage To High
Barometric Pressure Circuit Signal Voltage To Low
P0110 Intake Air Temperature Sensor Circuit Signal Too High
Intake Air Temperature Sensor Circuit Signal Too Low
Fig. 1 DATA LINK CONNECTOR
25a - 6 ON-BOARD DIAGNOSTICSRG

message the PCM will terminate engine operation,
or allow the engine to continue to operate.
3.2.7 SKIM ON-BOARD DIAGNOSTICS
The SKIM has been programmed to transmit and
monitor many different coded messages as well as
PCI Bus messages. This monitoring is called On
Board Diagnosis.
Certain criteria must be met for a diagnostic
trouble code to be entered into the SKIM memory.
The criteria may be a range of; Input voltage, PCI
Bus message, or coded messages to the SKIM. If all
of the criteria for monitoring a circuit or function
are met and a fault is sensed, a diagnostic trouble
code will be stored in the SKIM memory.
3.2.8 SKIS OPERATION
When ignition power is supplied to the SKIM, the
SKIM performs an internal self-test. After the self-
test is completed, the SKIM energizes the antenna
(this activates the transponder chip) and sends a
challenge to the transponder chip. The transponder
chip responds to the challenge by generating an
encrypted response message using the following:
Secret Key -This is an electronically stored
value (identification number) that is unique to each
SKIS. The secret key is stored in the SKIM, PCM
and all ignition key transponders.
Challenge- This is a random number that is
generated by the SKIM at each ignition key cycle.
The secret key and challenge are the two vari-
ables used in the algorithm that produces the
encrypted response message. The transponder uses
the crypto algorithm to receive, decode and respond
to the message sent by the SKIM. After responding
to the coded message, the transponder sends a
transponder I.D. message to the SKIM. The SKIM
compares the transponder I.D. to the available valid
key codes in the SKIM memory (8 key maximum at
any one time). After validating the key ignition the
SKIM sends a PCI Bus message called a Seed
Request to the engine controller then waits for a
PCM response. If the PCM does not respond, the
SKIM will send the seed request again. After three
failed attempts the SKIM will stop sending the seed
request and store a trouble code. If the PCM sends
a seed response, the SKIM sends a valid/invalid key
message to the PCM. This is an encrypted message
that is generated using the following:
VIN -Vehicle Identification Number
Seed -This is a random number that is generated
by the PCM at each ignition key cycle.
The VIN and seed are the two variables used in
the rolling code algorithm that encrypts the valid/
invalid key message. The PCM uses the rolling code
algorithm to receive, decode and respond to the
valid/invalid key message sent by the SKIM. Aftersending the valid/invalid key message the SKIM
waits 3.5 seconds for a PCM status message from
the PCM. If the PCM does not respond with a valid
key message to the SKIM, a fault is detected and a
trouble code is stored.
The SKIS incorporates a VTSS LED located on
the instrument panel upper cover. The LED re-
ceives switched ignition voltage and is hardwired to
the body control module. The LED is actuated when
the SKIM sends a PCI Bus message to the body
controller requesting the LED on. The body control-
ler then provides the ground for the LED. The
SKIM will request VTSS LED operation for the
following:
± bulb checks at ignition on
± to alert the vehicle operator to a SKIS mal-
function
± customer key programming mode
For all faults except transponder faults and VTSS
LED remains on steady. In the event of a transpon-
der fault the LED flashes at a rate of 1 Hz (once per
second). If a fault is present the LED will remain on
or flashing for the complete ignition cycle. If a fault
is stored in SKIM memory which prevents the
system from operating properly, the PCM will allow
the engine to start and run (for 2 seconds) up to six
times. After the sixth attempt, the PCM disables
the starter relay until the fault is corrected.
3.2.9 PROGRAMMING THE POWERTRAIN
CONTROL MODULE
Important Note:Before replacing the PCM for a
failed driver, control circuit or ground circuit, be
sure to check the related component/circuit integ-
rity for failures not detected due to a double fault in
the circuit. Most PCM driver/control circuit failures
are caused by internal failure to components (i.e.
12-volt pull-ups, drivers and ground sensors). These
failures are difficult to detect when a double fault
has occurred and only one DTC has set.
NOTE: IF THE PCM AND THE SKIM ARE
REPLACED AT THE SAME TIME, PROGRAM
THE VIN INTO THE PCM FIRST. ALL VEHICLE
KEYS WILL THEN NEED TO BE REPLACED
AND PROGRAMMED TO THE NEW SKIM.
The SKIS Secret Key is an I.D. code that is
unique to each SKIS. This code is programmed and
stored in the SKIM, engine controller and transpon-
der chip (ignition key). When replacing the PCM it
is necessary to program the secret key into the
PCM.
1. Turn the ignition on (transmission in park/
neutral).
2. Use the DRB and select THEFT ALARM, SKIM
then MISCELLANEOUS.
6
GENERAL INFORMATION

TEST ACTION APPLICABILITY
3 With the DRBIIIt, perform the SRI Memory Test a second time.
NOTE: Retest the SRI Memory two more times.
Does the DRBIIItdisplay Write Refused again?All
Ye s®Replace and program the Powertrain Control Module in accor-
dance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER-1.
No®Test Complete.
4 With the DRBIIIt, perform the SRI Memory Test.
Does the DRBIIItdisplay SRI Mileage Invalid?All
Ye s®Update the mileage and retest the SRI Memory.
Perform POWERTRAIN VERIFICATION TEST VER-1.
No®Go To 5
5 Compare the SRI Mileage stored with the Instrument Panel Odometer.
Is the mileage within the specified range displayed on the DRBIIIt?All
Ye s®Test Complete.
No®Update the mileage and retest the SRI Memory.
Perform POWERTRAIN VERIFICATION TEST VER-1.
31
COMMUNICATION
P1696-PCM FAILURE EEPROM WRITE DENIED ÐContinued

> Transmission Simulator (Miller # 8333)
> Transmission Simulator (Miller # 8333-1)
Adapter harness kit and panel overlay for FWD
vehicles.
> Jumper wires
> Test Light (minimum of 25 ohms of resistance)
> Ohmmeter
> Voltmeter
> Pressure gauge (0-300 PSI)
6.0 GLOSSARY OF TERMS
6.1 ACRONYMS
BCMBody Control Module
CKTCircuit
CVIClutch Volume Index
DLCData Link Connector
DRBIIItDiagnostic Readout Box
DTCDiagnostic Trouble Code
EATXElectronic Automatic Transaxle
EMCCElectronically Modulated Converter
Clutch
FCMFront Control Module (part of the
IPM system)
IODIgnition off-draw
IPMIntelligent Power Module
IRTIntelligent Recovery Timer
ISSInput Speed Sensor
LEDLight Emitting Diode
LRLow/reverse Clutch or Pressure
Switch
LULockupMICMechanical Instrument Cluster
MILMalfunction Indicator Lamp
OBDIIOn Board Diagnostics
ODOverdrive Clutch or Pressure
Switch
OSSOutput Speed Sensor
PCMPowertrain Control Module
PEMCCPartial Electronically Modulated
Converter Clutch
PLUPartial Lockup
REVReverse Clutch
SLPKSolenoid Pack
SSVSolenoid Switch Valve
SWSwitch
TCCTorque Converter Clutch
TCMTransmission Control Module
TPThrottle Position
TRDTorque Reduction
TRSTransmission Range Sensor
UDUnderdrive Clutch
2-42nd and 4th gear Clutch or Pres-
sure Switch
6.2 DEFINITIONS
OBDII (EURO STAGE III OBD) Trip - A vehicle
start and drive cycle such that all once per trip
diagnostic monitors have run.
Key Start - A vehicle start and run cycle of at least
20 seconds.
Warm-up Cycle - A vehicle start and run cycle
such that the engine coolant must rise to at least
71C (160ÉF) and must rise by at least 4.4C (40ÉF)
from initial start up. To count as a warm-up cycle,
no DTC may occur during the cycle.
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GENERAL INFORMATION