Page 425 of 4284

TEST ACTION APPLICABILITY
4Note: Ensure there is PCI Bus communication with other modules on the
vehicle before proceeding. If not, refer to the symptom list from the menu
and repair as necessary.
Disconnect the Thatcham Alarm Module C1 harness connector.
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 the chassis ground. Connect the Red lead to the PCI Bus
circuit in the Thatcham Alarm Module 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®Go To 5
No®Repair the PCI Bus circuit for an open.
Perform BODY VERIFICATION TEST - VER 1.
5 If there are no possible causes remaining, view repair. All
Repair
Replace the Thatcham Alarm Module in accordance with the
service information.
Perform BODY VERIFICATION TEST - VER 1.
396
COMMUNICATION
*BUS +/- SIGNALS OPEN OR NO RESPONSE FROM THATCHAM ALARM
MODULE Ð
Continued
Page 426 of 4284

Symptom:
*NO RESPONSE FROM CABIN HEATER ASSIST - DIESEL ONLY
POSSIBLE CAUSES
ATTEMPT TO COMMUNICATE WITH THE ECM
FUSED B+ CIRCUIT OPEN
GROUND CIRCUIT OPEN
SCI TRANSMIT CIRCUIT OPEN
CABIN HEATER ASSIST
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRB, attempt to communicate with the ECM.
Was the DRB able to I/D or communicate with the ECM?All
Ye s®Go To 2
No®Refer to the symptom list for problems related to no communica-
tion with the ECM.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
2 Turn the ignition off.
Disconnect the Cabin Heater Assist C2 harness connector.
Using a 12-volt test light connected to ground, probe the Fused B+ circuit.
Is the test light illuminated?All
Ye s®Go To 3
No®Check the IPM Fuse #15 for an open. If open, check for a short to
ground on the Fused B+ circuit. If not open, repair the Fused B+
circuit for an open.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
3 Turn the ignition off.
Disconnect the Cabin Heater Assist C2 harness connector.
Measure the resistance between ground and the ground circuit.
Is the resistance below 5.0 ohms?All
Ye s®Go To 4
No®Repair the ground circuit for an open.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
4 Turn the ignition off.
Disconnect the Cabin Heater Assist C1 harness connector.
Disconnect the DRB from the DLC.
Measure the resistance of the SCI Transmit circuit between the Cabin Heater Assist
connector and the DLC.
Is the resistance below 5.0 ohms?All
Ye s®Go To 5
No®Repair the SCI Transmit circuit for an open.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
397
COMMUNICATION
Page 427 of 4284
TEST ACTION APPLICABILITY
5 If there are no possible causes remaining, view repair. All
Repair
Replace the Cabin Heater Assist in accordance with the service
information.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
398
COMMUNICATION
*NO RESPONSE FROM CABIN HEATER ASSIST - DIESEL ONLY Ð
Continued
Page 428 of 4284

Symptom:
*NO RESPONSE FROM CONTROLLER ANTILOCK BRAKE
POSSIBLE CAUSES
NO RESPONSE FROM CAB
GROUND CIRCUIT OPEN
OPEN FUSED IGNITION SWITCH OUTPUT CIRCUIT
OPEN PCI BUS CIRCUIT
CONTROLLER ANTILOCK BRAKE
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, attempt to communicate with the Airbag Control Module (ACM).
With the DRB, attempt to communicate with the Body Control Module (BCM).
Was the DRB able to I/D or establish communications with either of the modules?All
Ye s®Go To 2
No®Refer to the Communications category and perform the symptom
PCI Bus Communication Failure.
Perform ABS VERIFICATION TEST - VER 1.
2 Turn the ignition off.
Disconnect the CAB harness connector.
Measure the resistance between ground and both ground circuits.
Is the resistance below 5.0 ohms for both measurements?All
Ye s®Go To 3
No®Repair the ground circuit(s) for an open.
Perform ABS VERIFICATION TEST - VER 1.
3 Turn the ignition off.
Disconnect the CAB harness connector.
Turn the ignition on.
Using a 12-volt test light connected to ground, probe the Fused Ignition Switch
Output circuit.
Is the test light illuminated?All
Ye s®Go To 4
No®Repair the Fused Ignition Switch Output circuit for an open.
Perform ABS VERIFICATION TEST - VER 1.
399
COMMUNICATION
Page 429 of 4284

TEST ACTION APPLICABILITY
4Note: Ensure there is PCI Bus communication with other modules on the
vehicle before proceeding. If not, refer to the symptom list from the menu
and repair as necessary.
Disconnect the CAB harness connector.
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 the chassis ground. Connect the Red lead to the PCI Bus
circuit in the CAB 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®Go To 5
No®Repair the PCI Bus circuit for an open.
Perform ABS VERIFICATION TEST - VER 1.
5 If there are no possible causes remaining, view repair. All
Repair
Replace the Controller Antilock Brake in accordance with the
Service Information.
Perform ABS VERIFICATION TEST - VER 1.
400
COMMUNICATION
*NO RESPONSE FROM CONTROLLER ANTILOCK BRAKE ÐContinued
Page 430 of 4284

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.
401
COMMUNICATION
Page 431 of 4284

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
402
COMMUNICATION
Page 432 of 4284
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.
403
COMMUNICATION
*NO RESPONSE FROM ECM (SCI ONLY) - DIESEL ONLY ÐContinued