
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

4.0 DISCLAIMERS, SAFETY,
WARNINGS
4.1 DISCLAIMERS
All information, illustrations, and specifications
contained in this manual are based on the latest
information available at the time of publication.
The right is reserved to make changes at any time
without notice.
4.2 SAFETY
4.2.1 TECHNICIAN SAFETY INFORMATION
WARNING: ENGINES PRODUCE CARBON
MONOXIDE THAT IS ODORLESS, CAUSES
SLOWER REACTION TIME, AND CAN LEAD
TO SERIOUS INJURY. WHEN THE ENGINE IS
OPERATING, KEEP SERVICE AREAS WELL
VENTILATED OR ATTACH THE VEHICLE
EXHAUST SYSTEM TO THE SHOP EXHAUST
REMOVAL SYSTEM.
Set the parking brake and block the wheels before
testing or repairing the vehicle. It is especially
important to block the wheels on front wheel drive
vehicles; the parking brake does not hold the drive
wheels.
When servicing a vehicle, always wear eye pro-
tection, and remove any metal jewelry such as
watchbands or bracelets that might make electrical
contact.
When diagnosing a powertrain system problem,
it is important to follow approved procedures where
applicable. These procedures can be found in the
service manual. Following these procedures is very
important to the safety of individuals performing
diagnostic tests.
4.2.2 VEHICLE PREPARATION FOR
TESTING
Make sure the vehicle being tested has a fully
charged battery. If it does not, false diagnostic codes
or error messages may occur.
4.2.3 SERVICING SUB-ASSEMBLIES
Some components of the powertrain system are
intended to be serviced as an assembly only. At-
tempting to remove or repair certain system sub-
components may result in personal injury and/or
improper system operation. Only those components
with approved repair and installation procedures in
the service manual should be serviced.
4.2.4 DRBIIITSAFETY INFORMATION
WARNING: EXCEEDING THE LIMITS OF THE
DRBIIITMULTIMETER IS DANGEROUS. IT
CAN EXPOSE YOU TO SERIOUS OR
POSSIBLY FATAL INJURY. CAREFULLY
READ AND UNDERSTAND THE CAUTIONS
AND SPECIFICATION LIMITS.
Follow the vehicle manufacturer 's service specifi-
cations at all times.
²Do not use the DRBIIItif it has been damaged.
²Do not use the test leads if the insulation is
damaged or if metal is exposed.
²To avoid electrical shock, do not touch the test
leads, tip or the circuit being tested.
²Choose the proper range and function for the
measurement. Do not try voltage or current mea-
surements that may exceed the rated capacity.
²Do not exceed the limits shown in the table below:
FUNCTION INPUT LIMIT
Volts 0-500 peak volts AC
0-500 volts DC
Ohms (Resistance)* 0-1.12 megohms
Frequency Measure
Frequency Generated0-10 kHz
Temperature -58 - +1100ÉF
-50 - +600ÉC
* Ohms cannot be measured if voltage is present.
Ohms can be measured only in a non-powered
circuit.
²Voltage between any terminal and ground must
not exceed 500v DC or 500v peak AC.
²Use caution when measuring voltage above 25v
DC or 25v AC.
²The circuit being tested must be protected by a 10
amp fuse or circuit breaker.
²Use the low current shunt to measure circuits up
to 10 amps. Use the high current shunt to mea-
sure circuits exceeding 10 amps.
²When testing for the presence of voltage or cur-
rent, make sure the meter is functioning cor-
rectly. Take a reading of a known voltage or
current before accepting a zero reading.
²When measuring current, connect the meter in
series with the load.
²Disconnect the live test lead before disconnecting
the common test lead.
7
GENERAL INFORMATION

Symptom:
*NO RESPONSE FROM ECM (PCI BUS) - DIESEL ONLY
POSSIBLE CAUSES
ECM PCI NO RESPONSE
PCI BUS CIRCUIT OPEN
ENGINE CONTROL MODULE
TEST ACTION APPLICABILITY
1 Turn the ignition on.
NOTE: As soon as one or more module communicates with the DRB, answer
the question.
With the DRB, enter Body then Body Computer.
With the DRB, enter Anti-Lock Brakes.
With the DRB, enter Body then Electro/Mechanical Cluster (MIC).
With the DRB, enter Passive Restraints then Airbag.
Were you able to establish communications with any of the modules?All
Ye s®Go To 2
No®Refer to symptom PCI Bus Communication Failure in the Com-
munications category.
Perform ROAD TEST VERIFICATION - VER-2.
2 With the DRB read ECM Diagnostic Trouble Codes. This is to ensure power and
grounds to the ECM are operational.
NOTE: If the DRB will not read ECM DTC's, follow the NO RESPONSE TO
ECM (SCI only) symptom path, if vehicle will start. For NO START Condi-
tions follow the no start symptom in the Starting category.
Turn the ignition off.
Disconnect the ECM harness connectors.
Use Scope input cable CH7058, Cable to Probe adapter CH7062, and the red and
black test probes.
Connect the scope input cable to the channel one connector on the DRB. Attach the
red and black leads and the cable to probe adapter to the scope input cable.
With the DRBIIItselect Pep Module Tools.
Select lab scope.
Select Live Data.
Select 12 volt square wave.
Press F2 for Scope.
Press F2 and use the down arrow to set voltage range to 20 volts. Press F2 again
when complete.
Connect the Black lead to ground. Connect the Red lead to the PCI Bus circuit in the
ECM connector.
Turn the ignition on.
Observe the voltage display on the DRB Lab Scope.
Does the voltage pulse from 0 to approximately 7.5 volts?All
Ye s®Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
No®Repair the PCI Bus circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
10
COMMUNICATION

Symptom:
*NO RESPONSE FROM ECM (SCI ONLY) - DIESEL ONLY
POSSIBLE CAUSES
CHECK ECM POWERS AND GROUNDS
CABIN HEATER ASSIST
SCI TRANSMIT CIRCUIT SHORTED TO VOLTAGE
SCI TRANSMIT CIRCUIT SHORTED TO GROUND
SCI TRANSMIT CIRCUIT OPEN
ENGINE CONTROL MODULE
TEST ACTION APPLICABILITY
1 Perform the symptom Checking ECM Power and Ground Circuits in the Driveability
category.
Did the vehicle pass this test?All
Ye s®Go To 2
No®Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
2 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the DRB from the DLC.
Measure the resistance between ground and the SCI Transmit circuit.
Is the resistance below 5.0 ohms?All
Ye s®Go To 3
No®Go To 4
3 Turn the ignition off.
Disconnect the Cabin Heater Assist C1 harness connector.
Measure the resistance between ground and the SCI Transmit circuit.
Is the resistance below 5.0 ohms?All
Ye s®Repair the SCI Transmit circuit for a short to ground.
Perform ROAD TEST VERIFICATION - VER-2.
No®Replace the Cabin Heater Assist in accordance with the service
information.
Perform ROAD TEST VERIFICATION - VER-2.
4 Turn the ignition off.
Disconnect the DRB from the DLC.
Disconnect the ECM harness connectors.
Disconnect the Cabin Heater Assist C1 harness connector.
Turn the ignition on.
Measure the voltage of the SCI Transmit circuit at the DLC connector (cav 7).
Is the voltage above 1.0 volt?All
Ye s®Repair the SCI Transmit circuit for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 5
11
COMMUNICATION

TEST ACTION APPLICABILITY
5 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the DRB from the DLC.
Measure the resistance of the SCI Transmit circuit between the ECM connector and
the DLC.
Is the resistance below 5.0 ohms?All
Ye s®Go To 6
No®Repair the SCI Transmit circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
6 If there are no possible causes remaining, view repair. All
Repair
Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
12
COMMUNICATION
*NO RESPONSE FROM ECM (SCI ONLY) - DIESEL ONLY ÐContinued

TEST ACTION APPLICABILITY
3 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Remove the ECM/PCM Relay from the PDC.
Connect a jumper wire between cavity 30 and cavity 87 of the ECM/PCM Relay
connector.
Turn the ignition on.
Measure the voltage of the MAF Sensor Signal circuit.
Is the voltage above 1.0 volt?All
Ye s®Repair the MAF Sensor Signal circuit for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 4
4 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the MAF Sensor Signal circuit.
Is the resistance below 10.0 ohms?All
Ye s®Go To 5
No®Repair the MAF Sensor Signal circuit for an open
Perform ROAD TEST VERIFICATION - VER-2.
5 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between ground and the MAF Sensor Signal circuit.
Is the resistance below 1000 ohms?All
Ye s®Repair the MAF Sensor Signal circuit for a short to ground.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 6
6 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between the MAF Sensor Signal circuit and the Sensor
Ground circuit at of the MAF Sensor harness connector.
Is the resistance below 1000 ohms?All
Ye s®Repair the MAF Sensor Signal for a short to Sensor Ground .
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 7
7 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Connect a jumper wire between MAF Sensor Signal circuit and the 5-volt supply
circuit at the MAF Sensor harness connector .
With the DRBIII, read the MAF VOLTS.
Does the DRBIII display between 4.0 and 5.5 volts?All
Ye s®Go To 8
No®Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
15
DRIVEABILITY - DIESEL
P0100-MASS AIR FLOW SENSOR PLAUSIBILITY ÐContinued

TEST ACTION APPLICABILITY
8 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the Sensor Ground circuit between the MAF Sensor and
the ECM.
Is the resistance below 10.0 ohms?All
Ye s®Go To 9
No®Repair the Sensor Ground circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
9 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Measure the voltage between the 5-volt Supply circuit and the Sensor Ground circuit
at the MAF Sensor harness connector.
Is the voltage above 4.5 volts?All
Ye s®Go To 10
No®Replace and program the ECM in accordance with the Service
Information.
Perform ROAD TEST VERIFICATION - VER-2.
10 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
With the DRBIIIt, actuate the ECM/PCM Relay.
Measure the voltage of the 12-volt Supply circuit at the MAF Sensor harness
connector
Is the voltage above 10.0 volts?All
Ye s®Go To 11
No®Repair the ECM/PCM Relay Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
11 Turn the ignition off.
NOTE: Inspect the turbocharger inlet tube between the MAF Sensor and the
Turbocharger. Ensure the airflow tube properly is secured at each end and
that there is no damage, restrictions or air leaks in the tube.
With a voltmeter, backprobe the MAF Sensor Signal circuit at the MAF Sensor
harness connector.
Allow the engine to idle for at least 2 minutes.
NOTE: The engine speed must be approximately 900 rpm for this test to be
valid.
Is the voltage between 2.1 and 2.7 volts?All
Ye s®Go To 12
No®Replace the Mass Air Flow Sensor in accordance with the Service
Information.
Perform ROAD TEST VERIFICATION - VER-2.
16
DRIVEABILITY - DIESEL
P0100-MASS AIR FLOW SENSOR PLAUSIBILITY ÐContinued

TEST ACTION APPLICABILITY
12 Turn the ignition off.
NOTE: Inspect the turbocharger inlet tube between the MAF Sensor and the
Turbocharger. Ensure the airflow tube properly is secured at each end and
that there is no damage, restrictions or air leaks in the tube.
With a voltmeter, backprobe the MAF Sensor Signal circuit at the MAF Sensor
harness connector.
With the engine at operating temperature, depress the throttle completely to the Full
throttle position for 5 seconds and note the voltmeter reading.
Is the voltage between 3.1 and 3.7 volts?All
Ye s®Test Complete.
No®Replace the Mass Air Flow Sensor in accordance with the Service
Information.
Perform ROAD TEST VERIFICATION - VER-2.
13 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the 5-volt Supply circuit.
Is the resistance below 10.0 ohms?All
Ye s®Go To 14
No®Repair the 5-volt Supply circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
14 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between the 5-volt Supply circuit and the Sensor Ground
circuit at the MAF Sensor harness connector.
Is the resistance above 1000 ohms?All
Ye s®Go To 15
No®Repair the 5-volt Supply circuit for a short to the Sensor Ground
circuit.
Perform ROAD TEST VERIFICATION - VER-2.
15 Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between ground and the 5-volt Supply circuit at the MAF
harness connector.
Is the resistance below 1000 ohms?All
Ye s®Repair the 5-volt Supply circuit for a short to ground.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 16
17
DRIVEABILITY - DIESEL
P0100-MASS AIR FLOW SENSOR PLAUSIBILITY ÐContinued