Jeep XJ. Manual — part 595
Symptom:
*NO RESPONSE FROM ECM AND PCM (DIESEL ONLY)
POSSIBLE CAUSES
ATTEMPT TO COMMUNICATE WITH ANOTHER VEHICLE
CHECK ECM POWERS AND GROUNDS
POWERTRAIN CONTROL MODULE - SCI TRANSMIT
CONTROLLER ANTILOCK BRAKE - SCI TRANSMIT
SCI TRANSMIT CIRCUIT SHORTED TO VOLTAGE
SCI CIRCUITS SHORTED TOGETHER
SCI TRANSMIT CIRCUIT SHORTED TO GROUND
SCI TRANSMIT CIRCUIT OPEN
GROUND CIRCUITS AT DLC OPEN
ENGINE CONTROL MODULE
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
Connect the DRB to another vehicle.
Will the DRB communicate with this vehicle?
All
Yes
→
No
→
Repair or replace the DRB or DRB cable as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
2
Perform the symptom Checking ECM and PCM Power and Ground Circuits in the
Driveability category.
Did the vehicle pass this test?
All
Yes
→
No
→
Repair as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
3
Turn the ignition off.
NOTE: Reconnect all previously disconnected components.
Disconnect the PCM harness connectors.
Turn the ignition on.
With the DRB, attempt to communicate with the ECM.
Was the DRB able to communicate with the ECM?
All
Yes
→
Replace the Powertrain Control Module.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
No
→
32
COMMUNICATION
TEST
ACTION
APPLICABILITY
4
Turn the ignition off.
Disconnect the CAB harness connector.
Turn the ignition on.
With the DRB, attempt to communicate with the ECM.
Was the DRB able to communicate with the ECM?
All
Yes
→
Replace the Controller Antilock Brake.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
No
→
5
Turn the ignition off.
Disconnect the DRB from the DLC.
Disconnect the PCM harness connectors.
Disconnect the ECM harness connectors.
Disconnect the CAB harness connector.
Turn the ignition on.
Measure the voltage of the SCI Transmit circuit at the DLC connector.
Is the voltage above 1.0 volt?
All
Yes
→
Repair the SCI Transmit circuit for a short to voltage.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
No
→
6
Turn the ignition off.
Disconnect the DRB from the DLC.
Disconnect the PCM harness connectors.
Disconnect the ECM harness connectors.
Disconnect the CAB harness connector.
Measure the resistance between the SCI Transmit circuit and the SCI Receive circuit
at the PCM connector.
Is the resistance below 5.0 ohms?
All
Yes
→
Repair the short between the SCI Transmit and the SCI Receive
circuits.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
No
→
7
Turn the ignition off.
Disconnect the DRB from the DLC.
Disconnect the PCM harness connectors.
Disconnect the ECM harness connectors.
Disconnect the CAB harness connector.
Measure the resistance between ground and the SCI Transmit circuit at the DLC.
Is the resistance below 5.0 ohms?
All
Yes
→
Repair the SCI Transmit circuit for a short to ground.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
No
→
33
COMMUNICATION
*NO RESPONSE FROM ECM AND PCM (DIESEL ONLY) —
Continued
TEST
ACTION
APPLICABILITY
8
Turn the ignition off.
Disconnect the DRB from the DLC.
Disconnect the ECM harness connectors.
Measure the resistance of the SCI Transmit circuit between the ECM connector and
the DLC.
Is the resistance below 5.0 ohms?
All
Yes
→
No
→
Repair the SCI Transmit circuit for an open.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
9
Turn the ignition off.
Disconnect the DRB from the DLC.
Disconnect the negative battery cable.
Measure the resistance between ground and both ground circuits at the DLC.
Is the resistance below 5.0 ohms for each measurement?
All
Yes
→
No
→
Repair the ground circuit that measured above 5.0 ohms for an
open.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
10
If there are no possible causes remaining, view repair.
All
Repair
Replace the Engine Control Module.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
34
COMMUNICATION
*NO RESPONSE FROM ECM AND PCM (DIESEL ONLY) —
Continued
Symptom:
*NO RESPONSE FROM POWERTRAIN CONTROL MODULE (DIE-
SEL ONLY)
POSSIBLE CAUSES
ATTEMPT TO COMMUNICATE WITH THE ECM
CHECK PCM POWERS AND GROUNDS
SCI RECEIVE CIRCUIT SHORTED TO GROUND
SCI RECEIVE CIRCUIT OPEN
SCI TRANSMIT CIRCUIT OPEN
POWERTRAIN CONTROL MODULE
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRB attempt to communicate with the ECM.
Was the DRB able to communicate with the ECM?
All
Yes
→
No
→
Refer to symptom list for problems related to No Response From
ECM and PCM.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
2
Perform the symptom Checking ECM and PCM Power and Ground Circuits in the
Driveability category.
Did the vehicle pass this test?
All
Yes
→
No
→
Repair as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
3
Turn the ignition off.
Disconnect the PCM C3 harness connector.
Disconnect the DRB from the DLC.
Measure the resistance between ground and the SCI Receive circuit.
Is the resistance below 5.0 ohms?
All
Yes
→
Repair the SCI Receive circuit for a short to ground.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
No
→
4
Turn the ignition off.
Disconnect the PCM C3 harness connector.
Measure the resistance of the SCI Receive circuit between the PCM C3 connector and
the DLC.
Is the resistance below 5.0 ohms?
All
Yes
→
No
→
Repair the SCI Receive circuit for an open.
Perform POWERTRAIN VERIFICATION TEST VER - 1.
35
COMMUNICATION
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