engine CHRYSLER VOYAGER 2001 Service Manual

TEST ACTION APPLICABILITY
3 Turn the ignition off.
Disconnect the CAB connector.
Note: Check connector - Clean/repair as necessary.
Start the engine.
Raise engine speed above 1,800 RPM.
Measure the battery voltage.
Is the voltage above 16.5 volts ?All
Ye s®Refer to appropriate service information for charging system
testing and repair.
Perform ABS VERIFICATION TEST - VER 1.
No®Go To 4
4 Turn the ignition off.
Disconnect the CAB connector.
Note: Check connector - Clean/repair as necessary.
Measure the resistance of the ground circuits.
Is the resistance below 1.0 ohm?All
Ye s®Go To 5
No®Repair the Ground circuit for an open.
Perform ABS VERIFICATION TEST - VER 1.
5 If there are no potential causes remaining, view repair. All
Repair
Replace the Controller Antilock Brake.
Perform ABS VERIFICATION TEST - VER 1.
6 Turn the ignition off.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wire harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Refer to any Hotline letters or Technical Service Bulletins that may apply.
Were any problems found?All
Ye s®Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No®Test Complete.
29
BRAKES (CAB)
SYSTEM OVERVOLTAGE ÐContinued

Symptom:
SYSTEM UNDERVOLTAGE
When Monitored and Set Condition:
SYSTEM UNDERVOLTAGE
When Monitored: Ignition on. The CAB monitors the Fused Ignition Switch Output
circuit voltage above 10 km/h (6 mph) every 7 milliseconds for proper system voltage.
Set Condition: If the voltage is below 9.5 volts, the Diagnostic Trouble Code (DTC) is set.
POSSIBLE CAUSES
BATTERY VOLTAGE LOW
INTERMITTENT DTC
FUSED IGNITION SWITCH OUTPUT CIRCUIT HIGH RESISTANCE
CAB - INTERNAL FAULT
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, erase DTC's.
Turn the ignition off.
Turn the ignition on.
Start the engine.
Drive the vehicle above 16 km/h (10 mph) for at least 20 seconds.
Stop the vehicle
With the DRBIIIt, read DTC's.
Does the DRBIIItdisplay System Undervoltage DTC?All
Ye s®Go To 2
No®Go To 5
2 Engine Running.
Measure the battery voltage.
Is the battery voltage below 10 volts?All
Ye s®Refer to appropriate service information for charging system
testing and repair.
Perform ABS VERIFICATION TEST - VER 1.
No®Go To 3
3 Disconnect the CAB harness connector.
Turn the ignition on.
Measure the voltage of the Fused Ignition Switch circuit.
Is the voltage above 10 volts?All
Ye s®Go To 4
No®Repair the Fused Ignition Switch Output Circuit for high resis-
tance
Perform ABS VERIFICATION TEST - VER 1.
30
BRAKES (CAB)

Verification Tests
ABS VERIFICATION TEST - VER 1 APPLICABILITY
1. Turn the ignition off.
2. Connect all previously disconnected components and connectors.
3. Ensure all accessories are turned off and the battery is fully charged.
4. Ensure that the Ignition is on, and with the DRBIII, erase all Diagnostic Trouble Codes from
ALL modules. Start the engine and allow it to run for 2 minutes and fully operate the system
that was malfunctioning.
5. Turn the ignition off and wait 5 seconds. Turn the ignition on and using the DRBIII, read
DTC's from ALL modules.
6. If any Diagnostic Trouble Codes are present, return to Symptom list and troubleshoot new
or recurring symptom.
7. If there are no DTC's present after turning ignition on, road test the vehicle for at least 5
minutes. Perform several antilock braking stops.
8. Caution: Ensure braking capability is available before road testing.
9. Again, with the DRBIIItread DTC's. If any DTC's are present, return to Symptom list.
10. If there are no Diagnostic Trouble Codes (DTC's) present, and the customer's concern can
no longer be duplicated, the repair is complete.
Are any DTC's present or is the original concern still present?All
Ye s®Repair is not complete, refer to appropriate symptom.
No®Repair is complete.
40
VERIFICATION TESTS

DIAGNOSTIC JUNCTION PORT - BLACK 16 WAYCAV CIRCUIT FUNCTION
1 D25 20WT/VT PCI BUS (PCM/SKIM)
2 D25 20WT/VT PCI BUS (HVAC)
3 D25 20WT/VT PCI BUS (RADIO)
4 D25 20WT/VT PCI BUS (ORC)
5 D25 20WT/VT PCI BUS (CLUSTER)
6 D25 20WT/VT PCI BUS (BCM)
7 D25 20WT/VT PCI BUS (DLC)
8 D25 20WT/VT PCI BUS (OVERHEAD CONSOLE)
9 D25 20WT/VT PCI BUS (IPM)
10 D25 20WT/VT PCI BUS (LSIACM)
11 D25 20WT/VT PCI BUS (MEMORY SEAT/MIRROR)
12 D25 20WT/VT PCI BUS (PWR DOOR/ LT, RT LIFTGATE)
13 D25 20WT/VT PCI BUS (RSIACM)
14 - -
15 - -
16 - -
INTELLIGENT POWER MODULE C4 - GRAY 10 WAYCAV CIRCUIT FUNCTION
1 Z127 12BK/DG GROUND
2 T750 12YL/GY ENGINE STARTER MOTOR RELAY OUTPUT
3 K342 16BR/WT AUTOMATIC SHUTDOWN RELAY OUTPUT
4 F500 18DG/PK (ANTILOCK
BRAKES)FUSED IGNITION SWITCH RELAY OUTPUT (RUN)
5- -
6 D25 16WT/VT (ANTILOCK
BRAKES)PCI BUS
7 A107 12TN/RD (ANTILOCK
BRAKES)FUSED B(+)
8 A111 12DG/RD (ANTILOCK
BRAKES)FUSED B(+)
9 A701 14BR/RD FUSED B(+)
10 - -
LEFT FRONT WHEEL SPEED SENSOR - BLACK 2 WAYCAV CIRCUIT FUNCTION
1 B9 18DG/LG LEFT FRONT WHEEL SPEED SENSOR SIGNAL
2 B8 18DG/TN LEFT FRONT WHEEL SPEED SENSOR 12 VOLT SUPPLY
C
O
N
N
E
C
T
O
R
P
I
N
O
U
T
S
48
CONNECTOR PINOUTS

TABLE OF CONTENTS - Continued
P0100-MASS AIR FLOW SENSOR SUPPLY VOLTAGE TOO HIGH OR LOW......13
P0105-BAROMETRIC PRESSURE CIRCUIT SIGNAL VOLTAGE TOO HIGH.......20
P0105-BAROMETRIC PRESSURE CIRCUIT SIGNAL VOLTAGE TOO LOW........20
P0606-ECM ERROR GATE ARRAY - COMMUNICATION.......................20
P0606-ECM ERROR GATE ARRAY - COMMUNICATION NOT VERIFIED..........20
P0606-ECM ERROR GATE ARRAY - QUANTITY STOP........................20
P0606-ECM ERROR RECOVERY HAS OCCURRED..........................20
P0606-ECM ERROR REDUNDANT OVERRUN MONITORING..................20
P1206-CALCULATED INJECTOR VOLTAGE TOO HIGH........................20
P1206-CALCULATED INJECTOR VOLTAGE TOO LOW........................20
P1601-CAPACITOR VOLTAGE 1 VOLTAGE TOO HIGH........................20
P1601-CAPACITOR VOLTAGE 1 VOLTAGE TOO LOW.........................20
P1606-AFTER RUN SHUT OFF ERROR-INJECTION POWERSTAGE............20
P1606-AFTER RUN SHUT OFF ERROR-ZERO QUANTITY.....................20
P1610-VOLTAGE REGULATOR SIGNAL VOLTAGE TOO HIGH..................20
P1610-VOLTAGE REGULATOR SIGNAL VOLTAGE TOO LOW..................20
P1680-EEPROM PLAUSIBILITY CHECKSUM ERROR.........................20
P1680-EEPROM PLAUSIBILITY CODE WORD INCORRECT OR MISSING........20
P1680-EEPROM PLAUSIBILITY COMMUNICATION ERROR....................20
P1680-EEPROM PLAUSIBILITY VARIATION NUMBER ERROR.................20
P1680-EEPROM PLAUSIBILITY VIN CHECKSUM ERROR.....................20
P1680-EEPROM PLAUSIBILITY WRITE ERROR..............................20
P1696-EEPROM MEMORY WRITE DENIED.................................20
P0110-INTAKE AIR TEMP SENSOR CIRCUIT SIGNAL VOLTAGE TOO HIGH......24
P0110-INTAKE AIR TEMP SENSOR CIRCUIT SIGNAL VOLTAGE TOO LOW.......27
P0115-ENGINE COOLANT TEMP SENSOR CIRCUIT SIGNAL
VOLTAGE TOO HIGH....................................................29
P0115-ENGINE COOLANT TEMP SENSOR CIRCUIT SIGNAL
VOLTAGETOO LOW ....................................................32
P0190-FUEL PRESS SENSOR CIRCUIT MALF SIGNAL VOLTAGE TOO HIGH.....34
P0190-FUEL PRESS SENSOR CIRCUIT MALF SIGNAL VOLTAGE TOO LOW.....38
P0190-FUEL PRESS SENSOR CIRCUIT MALF SUPPLY VOLTAGE
TOO HIGH OR LOW.....................................................40
P0195-OIL TEMP SENSOR CIRCUIT MALF SIGNAL VOLTAGE TOO HIGH........41
P0195-OIL TEMP SENSOR CIRCUIT MALF SIGNAL VOLTAGE TOO LOW........44
P0201-CYLINDER 1-INJECTOR CIRCUIT CURRENT DECREASE...............46
P0201-CYLINDER 1-INJECTOR CIRCUIT LOAD DROP........................46
P0201-CYLINDER 1-INJECTOR CIRCUIT OVERCURRENT HIGH SIDE...........46
P0201-CYLINDER 1-INJECTOR CIRCUIT OVERCURRENT LOW SIDE...........46
P0202-CYLINDER 2-INJECTOR CIRCUIT CURRENT DECREASE...............50
P0202-CYLINDER 2-INJECTOR CIRCUIT LOAD DROP........................50
P0202-CYLINDER 2-INJECTOR CIRCUIT OVERCURRENT HIGH SIDE...........50
P0202-CYLINDER 2-INJECTOR CIRCUIT OVERCURRENT LOW SIDE...........50
P0203-CYLINDER 3-INJECTOR CIRCUIT CURRENT DECREASE...............54
P0203-CYLINDER 3-INJECTOR CIRCUIT LOAD DROP........................54
P0203-CYLINDER 3-INJECTOR CIRCUIT OVERCURRENT HIGH SIDE...........54
P0203-CYLINDER 3-INJECTOR CIRCUIT OVERCURRENT LOW SIDE...........54
P0204-CYLINDER 4-INJECTOR CIRCUIT CURRENT DECREASE...............58
P0204-CYLINDER 4-INJECTOR CIRCUIT LOAD DROP........................58
P0204-CYLINDER 4-INJECTOR CIRCUIT OVERCURRENT HIGH SIDE...........58
P0204-CYLINDER 4-INJECTOR CIRCUIT OVERCURRENT LOW SIDE...........58
P0235-BOOST PRESSURE SENSOR PLAUSIBILITY..........................62
P0235-BOOST PRESSURE SENSOR SIGNAL VOLTAGE TOO HIGH.............64
ii

TABLE OF CONTENTS - Continued
P0703-BRAKE SWITCH SIGNAL CKTS PLAUS W/REDUNDANT CONTACT
AFTER INITIALIZATION.................................................149
P0833-CLUTCH PEDAL PLAUSIBILITY....................................153
P1130-FUEL RAIL PRESSURE MALFUNCTION LEAKAGE DETECTED..........155
P1130-FUEL RAIL PRESSURE MALFUNCTION PRESSURE TOO HIGH-SHUT
OFF .................................................................155
P1130-FUEL RAIL PRESSURE MALFUNCTION PRESSURE TOO LOW.........155
P1130-FUEL RAIL PRESSURE MALFUNCTION SOLENOID OPEN.............155
P1131-FUEL PRESSURE SOLENOID OPEN CIRCUIT........................158
P1131-FUEL PRESSURE SOLENOID PLAUSIBILITY IN AFTER-RUN............158
P1131-FUEL PRESSURE SOLENOID SHORT CIRCUIT.......................158
P1511-BATTERY SENSE LINE 1 VOLTAGE TOO HIGH.......................162
P1511-BATTERY SENSE LINE 1 VOLTAGE TOO LOW.......................164
P1605-IGNITION SWITCH PLAUSIBILITY..................................166
P1685-SKIM SYSTEM INVALID KEY CODE RECEIVED.......................168
P1685-SKIM SYSTEM INVALID SECRET KEY IN EEPROM....................168
P1685-SKIM SYSTEM KEY COMMUNICATION TIMED OUT...................168
P1685-SKIM SYSTEM SKIM ERROR......................................168
P1685-SKIM SYSTEM WRITE ACCESS TO EEPROM FAILURE................168
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY................170
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY WITH BRAKE
SWITCH..............................................................170
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY WITH
POTENTIOMETER.....................................................170
P2120-ACC PEDAL POSITION SENSOR 1 CKT SIGNAL VOLTAGE TOO HIGH . . .170
P2120-ACC PEDAL POSITION SENSOR 1 CKT SIGNAL VOLTAGE TOO LOW . . .170
P2120-ACC PEDAL POSITION SENSOR 1 CKT SUPPLY VOLTAGE TOO
HIGH OR LOW........................................................170
*CHECKING THE A/C CLUTCH OPERATION...............................179
*CHECKING THE ACCELERATOR PEDAL POSITION SENSOR CALIBRATION . . .181
*CHECKING THE BOOST PRESSURE SENSOR CALIBRATION................182
*CHECKING THE ECM POWER AND GROUND CIRCUITS....................183
*CHECKING THE EGR SYSTEM..........................................185
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION...................186
*CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR CALIBRATION . .193
*CHECKING THE ENGINE MECHANICAL SYSTEMS.........................194
*CHECKING THE GLOW PLUG OPERATION...............................195
*CHECKING THE LIFT PUMP MOTOR OPERATION.........................197
*CHECKING THE MAF SENSOR CALIBRATION.............................200
*CHECKING THE SPEED CONTROL OPERATION...........................201
*CHECKING THE VEHICLE SPEED SIGNAL................................204
*ENGINE CRANKS BUT WILL NOT START.................................207
*ENGINE WILL NOT CRANK.............................................210
VEHICLE THEFT/SECURITY
ANTENNA FAILURE....................................................214
COP FAILURE.........................................................214
EEPROM FAILURE.....................................................214
INTERNAL FAULT......................................................214
RAM FAILURE.........................................................214
SERIAL LINK INTERNAL FAULT..........................................214
STACK OVERFLOW FAILURE............................................214
PCM STATUS FAILURE.................................................216
iv

TABLE OF CONTENTS - Continued
SERIAL LINK EXTERNAL FAULT.........................................216
ROLLING CODE FAILURE...............................................218
VIN MISMATCH........................................................218
TRANSPONDER COMMUNICATION FAILURE..............................220
TRANSPONDER CYCLIC REDUNDANCY CHECK (CRC) FAILURE.............220
TRANSPONDER ID MISMATCH..........................................220
TRANSPONDER RESPONSE MISMATCH..................................220
VERIFICATION TESTS
VERIFICATION TESTS..................................................223
8.0 COMPONENT LOCATIONS..............................................227
8.1CONTROL MODULES.............................................227
8.2CONTROLS AND SOLENOIDS......................................227
8.3DATA LINK CONNECTOR..........................................227
8.4FUEL SYSTEM...................................................228
8.5RELAYS.........................................................228
8.6SENSORS.......................................................229
8.7SWITCHES......................................................230
9.0 CONNECTOR PINOUTS................................................231
A/C COMPRESSOR CLUTCH - LT. GRAY 2 WAY............................231
A/C PRESSURE SENSOR - GRAY 4 WAY..................................231
ACCELERATOR PEDAL POSITION SENSOR (DIESEL) - BLACK 10 WAY........231
BATTERY TEMPERATURE SENSOR (DIESEL) - BLACK 2 WAY................231
BOOST PRESSURE SENSOR (DIESEL) - BLACK 4 WAY.....................232
BRAKE LAMP SWITCH - BLACK 6 WAY...................................232
CAMSHAFT POSITION SENSOR (DIESEL) - BLACK 3 WAY...................232
CLUTCH PEDAL UPSTOP SWITCH (DIESEL) - RED 2 WAY...................232
CRANKSHAFT POSITION SENSOR (DIESEL) - BLACK 3 WAY................232
DATA LINK CONNECTOR - BLACK 16 WAY................................233
EGR SOLENOID (DIESEL) - LT. GRAY 2 WAY...............................233
ENGINE CONTROL MODULE C1 (DIESEL) - BLACK 81 WAY..................234
ENGINE CONTROL MODULE C1 (DIESEL) - BLACK 81 WAY..................235
ENGINE CONTROL MODULE C2 (DIESEL) - BLACK 40 WAY..................236
ENGINE COOLANT TEMP SENSOR (DIESEL) - BLUE 2 WAY.................236
ENGINE OIL PRESSURE SENSOR (DIESEL) - BLACK 3 WAY.................237
ENGINE OIL TEMPERATURE SENSOR (DIESEL) - BLACK 2 WAY.............237
FUEL HEATER (DIESEL) - BLACK 2 WAY..................................237
FUEL INJECTOR NO. 1 (DIESEL) - BLACK 2 WAY...........................237
FUEL INJECTOR NO. 2 (DIESEL) - BLACK 2 WAY...........................237
FUEL INJECTOR NO. 3 (DIESEL) - BLACK 2 WAY...........................238
FUEL INJECTOR NO. 4 (DIESEL) - BLACK 2 WAY...........................238
FUEL PRESSURE SENSOR (DIESEL) - BLACK 3 WAY.......................238
FUEL PRESSURE SOLENOID (DIESEL) - BLACK 2 WAY.....................238
GENERATOR - BLACK 2 WAY...........................................238
GLOW PLUG RELAY (DIESEL) - BLACK 4 WAY.............................239
INTELLIGENT POWER MODULE C3 (DIESEL) - YELLOW/RED 20 WAY.........239
LEFT SPEED CONTROL SWITCH - WHITE 2 WAY..........................239
LIFT PUMP MOTOR (DIESEL) - BLACK 2 WAY..............................239
MASS AIR FLOW SENSOR (DIESEL) - ORANGE 5 WAY......................240
v

1.0 INTRODUCTION
The procedures contained in this manual include
all the specifications, instructions and graphics
needed to diagnose engine control module (ECM)
and sentry key immobilizer system (SKIS) prob-
lems; they are no start, diagnostic trouble code
(DTC), and no trouble code problems for the ECM.
The diagnostics in this manual are based on the
trouble condition or symptom being present at the
time of diagnosis.
When repairs are required, refer to the appropri-
ate service information for the proper removal and
repair procedure.
Diagnostic procedures change every year. New
diagnostic systems may be added; carryover sys-
tems may be enhanced. IT IS RECOMMENDED
THAT YOU REVIEW THE ENTIRE MANUAL TO
BECOME FAMILIAR WITH ALL NEW AND
CHANGED DIAGNOSTIC PROCEDURES.
This manual is designed to begin all diagnosis at
the DTC TEST, which is located at the beginning of
Section 7.0. This will cover all the necessary re-
quirements to begin a logical diagnostic path for
each problem. If there is a diagnostic trouble code
(DTC) detected, it will direct you to the trouble code
test. If there are no DTCs present, it will direct you
by symptom to a no trouble code test.
This book reflects many suggested changes from
readers of past issues. After using this book, if you
have any comments or recommendations, please fill
out the form at the back of the book and mail it back
to us.
1.1 SYSTEM COVERAGE
This diagnostic procedures manual covers all
2001 RG body vehicles equipped with the 2.5L VM
diesel engine.
1.2 SIX-STEP TROUBLESHOOTING
PROCEDURE
Diagnosis of the engine control module (ECM)
and sentry key immobilizer system (SKIS) is done
in six basic steps:
²verification of complaint
²verification of any related symptom
²symptom analysis
²problem isolation
²repair of isolated problem
²verification of proper operation
NOTE: All tests in this manual should be per-
formed with the engine at operating temperature,
unless specified within a particular test.
2.0 IDENTIFICATION OF
SYSTEM
The ECM is located in the left side of the engine
compartment between the left front headlamp and
the intelligent power module. The sentry key immo-
bilizer module (SKIM) is located below the steering
column behind the steering wheel.
3.0 SYSTEM DESCRIPTION AND
FUNCTIONAL OPERATION
3.1 GENERAL DESCRIPTION
The 2.5L VM diesel engine system is equipped
with the latest in technical advances. The on-board
diagnostics incorporated in the engine control mod-
ule and SKIM are intended to assist the field
technician in repairing vehicle problems by the
quickest means.
The engine system incorporates a common rail
fuel delivery design. This design utilizes electroni-
cally controlled solenoid valve type fuel injectors.
Each injector is controlled individually by the ECM.
Injector timing and fuel quantity are controlled by
the ECM based on inputs from the various sensors.
The precision control of the injectors by the ECM
helps to reduce the engine noise, odor and smoke.
3.2 FUNCTIONAL OPERATION
3.2.1 ECM ON-BOARD DIAGNOSTICS
The ECM has been programmed to monitor many
different circuits of the diesel fuel injection system.
This monitoring is called on-board diagnostics.
Certain criteria must be met for a trouble code to
be entered into the ECM memory. The criteria may
be a range of: engine rpm, engine temperature, time
or other input signals to the ECM. If all of the
criteria for monitoring a system or circuit are met,
and a problem is sensed, then a DTC will be stored
in the ECM memory.
It is possible that a DTC for a monitored circuit
may not be entered into the ECM memory, even
though a malfunction has occurred. This may hap-
pen when the monitoring criteria has not been met.
The ECM compares input signal voltages from
each input device with specifications (the estab-
lished high and low limits of the input range) that
are programmed into it for that device. If the input
voltage is not within the specifications and other
trouble code criteria are met, a DTC will be stored
in the ECM memory.
1
GENERAL INFORMATION

3.2.2 ECM OPERATING MODES
As input signals to the ECM change, the ECM
adjusts its response to the output devices. For
example, the ECM must calculate a different fuel
quantity and fuel timing for engine idle condition
than it would for a wide open throttle condition.
There are several different modes of operation that
determine how the ECM responds to the various
input signals.
Ignition Switch On (Engine Off)
When the ignition switch is turned on, the ECM
activates the glow plug relay for a time period that
is determined by engine coolant temperature, atmo-
spheric temperature and battery voltage. The ECM
also activates the lift pump to prime the fuel sys-
tem.
Engine Start-up Mode
The ECM uses the engine temperature sensor
and the crankshaft position sensor (engine speed)
inputs to determine fuel injection quantity.
Normal Driving Modes
Engine idle, warm-up, acceleration, deceleration
and wide open throttle modes are controlled based
on all of the sensor inputs to the ECM. The ECM
uses these sensor inputs to adjust fuel quantity and
fuel injector timing.
Overheat Protection Mode
If engine temperature is above 106É C (223É F)
and vehicle speed is above 40 km/h (25 MPH) the
ECM will activate the high speed fan and will limit
fuel quantity for engine protection.
Limp-In Mode
If there is a fault detected with the accelerator
pedal position sensor, the ECM will set the engine
speed at 1100 RPM.
Overspeed Detection Mode
If the ECM detects engine RPM that exceeds
5000 RPM, the ECM will set a DTC in memory and
limit engine RPM to no more that 2500 RPM until
the DTC(s) is cleared.
After-Run Mode
The ECM transfers RAM information to ROM
and performs an Input/Output state check.
3.2.3 MONITORED CIRCUITS
The ECM is able to monitor and identify most
driveability related trouble conditions. Some cir-
cuits are directly monitored through ECM feedback
circuitry. In addition, the ECM monitors the voltage
state of some circuits and compares those stateswith expected values. Other systems are monitored
indirectly when the ECM conducts a rationality test
to identify problems.
Although most subsystems of the engine control
module are either directly or indirectly monitored,
there may be occasions when diagnostic trouble
codes are not immediately identified. For a trouble
code to set, a specific set of conditions must occur
and unless these conditions occur, a DTC will not
set.
3.2.4 SKIS OVERIVEW
The sentry key immobilizer system (SKIS) is
designed to prevent unauthorized vehicle opera-
tion. The system consists of a sentry key immobi-
lizer module (SKIM), ignition key(s) equipped with
a transponder chip and the ECM. When the ignition
switch is turned on, the SKIM interrogates the
ignition key. If the ignition key is Valid or Invalid,
the SKIM sends a PCI Bus message to the ECM
indicating ignition key status. Upon receiving this
message the ECM will terminate engine operation
or allow the engine to continue to operate.
3.2.5 SKIS ON-BOARD DIAGNOSTICS
The sentry key immobilizer module (SKIM) has
been programmed to transmit and monitor many
different coded messages as well as PCI Bus mes-
sages. This monitoring is called On-Board Diagnos-
tics. Certain criteria must be met for a DTC to be
entered into 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 detected, a DTC will be stored in the SKIM
memory.
3.2.6 SKIS OPERATION
When ignition power is supplied to the SKIM, the
SKIM performs an internal self-test. After the self-
test is complete, 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, ECM and all
ignition key transponders.
Challenge - This is a random number that is gen-
erated 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 SKIM. After responding to
the coded message, the transponder sends a tran-
2
GENERAL INFORMATION

sponder ID message to the SKIM. The SKIM com-
pares the transponder ID message to the available
valid key codes in SKIM memory (8 key maximum
at any one time). After validating the ignition key,
the SKIM sends a PCI Bus message called a seed
request to the ECM, then waits for the ECM re-
sponse. If the ECM 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 in memory. If the
ECM sends a seed response, the SKIM sends a
valid/invalid key message to the ECM. 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 ECM at each ignition key cycle.
The VIN and seed are two variables used in the
rolling code algorithm that encrypts the valid/
invalid key message. The ECM uses the rolling code
algorithm to receive, decode and respond to the
valid/invalid key message sent by the SKIM. After
sending the valid/invalid key message, the SKIM
waits 3.5 seconds for an ECM status message from
the ECM. If the ECM does not respond with a valid
key message to the SKIM, a fault is detected and a
code is stored.
The SKIS incorporates a warning lamp located in
the information center. The lamp receives switched
ignition voltage and is hardwired to the body con-
trol module. The lamp is actuated when the SKIM
sends a PCI Bus message to the body control
module requesting the lamp on. The body control
module then provides the ground for the lamp.
The SKIM will request lamp operation for the
following:
± bulb check at ignition on
± to alert the vehicle operator to a SKIS malfunc-
tion
± when the SKIM is in customer key programming
mode
For all faults except transponder faults the lamp
remains on steady. In the event of a transponder
fault the lamp will flash at a rate of 1Hz (once per
second). If a fault is present, the lamp 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 ECM will allow
the engine to start and idle for 2 seconds then stall.
This may occur up to six times. After the sixth
attempt, the ECM disables the starter relay until
the fault is corrected.
3.3 DIAGNOSTIC TROUBLE CODES
Each diagnostic trouble code (DTC) is diagnosed
by following a specific procedure. The diagnostic
test procedure contains step-by-step instruction fordetermining the cause of the DTC as well as no
trouble code problems. It is not necessary to per-
form all of the tests in this book to diagnose an
individual code.
Always begin diagnosis by reading the DTC's
using the DRBIIIt.
3.3.1 HARD CODE
A DTC that comes back within one cycle of the
ignition key is a hard code. This means that the
problem is current every time the ECM/SKIM
checks that circuit or function. Procedures in this
manual verify if the DTC is a hard code at the
beginning of each test. When the fault is not a hard
code, an intermittent test must be performed.
NOTE: If the DRBIIItdisplays faults for multiple
components (i.e. ECT, VSS, Oil Temp sensors) iden-
tify and check the shared circuits for possible prob-
lems before continuing (i.e. sensor grounds or 5-volt
supply circuits). Refer to the appropriate schematic
to identify shared circuits.
3.3.2 INTERMITTENT CODE
A DTC that is not current every time the ECM/
SKIM checks the circuit or function is an intermit-
tent code. Most intermittent DTCs are caused by
wiring or connector problems. Problems that come
and go like this are the most difficult to diagnose;
they must be looked for under specific conditions
that cause them. The following checks may assist
you in identifying a possible intermittent problem.
²Visually inspect the related wire harness connec-
tors. Look for broken, bent, pushed out, or cor-
roded terminals.
²Visually inspect the related wire harness. Look
for chafed, pierced, or partially broken wire.
²Refer to hotlines or technical service bulletins
that may apply.
NOTE: Electromagnetic (radio) interference can
cause an intermittent system malfunction. This
interference can interrupt communication between
the ignition key transponder and the SKIM.
3.3.3 ECM DIAGNOSTIC TROUBLE CODES
IMPORTANT NOTE:Before replacing the ECM
for a failed driver, control circuit or ground circuit,
be sure to check the related component/circuit in-
tegrity for failures not detected due to a double fault
in the circuit. Most ECM driver/control circuit fail-
ures are caused by internal failures to components
(i.e. relays and solenoids) and shorted circuits (i.e.
sensor pull-ups, drivers and ground circuits). These
faults are difficult to detect when a double fault has
occurred and only one DTC has set.
If the DRB displays faults for multiple compo-
nents (i.e. VSS, ECT, Batt Temp, etc.), identify and
3
GENERAL INFORMATION