U0252

U0252-LOST COMMUNICATION WITH TRAILER LIGHTING MODULE





For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.

- When Monitored:
With the ignition on.

Battery voltage between 10 and 16 volts.

IOD fuse installed.

Front Control Module (FCM) is configured correctly.

- Set Condition:
Bus messages not received from the Trailer Lighting Module (TM) for approximately 2 to 5 seconds.





1. VERIFY THE DIAGNOSTIC TROUBLE CODE (DTC) IS ACTIVE

NOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.

1. With the scan tool, read active DTCs.

Is this DTC active?

Yes

- Go To 2

No

- Refer to the Stored Lost Communication test procedure. Stored Lost Communication DTCs

2. CHECK FOR ANY OF THE FOLLOWING ACTIVE DTC'S
1. With the scan tool, read active DTCs from all modules.

NOTE: Check for FCM configuration, CAN B or C hardware electrical, VIN Missing/Mismatch, battery or ignition related DTCs.

Does the scan tool display any active DTCs to the conditions listed above?

Yes

- Go to and perform the appropriate diagnostic procedure.

No

- Go To 3

3. VERIFY THAT THE TM IS ACTIVE ON THE BUS
1. Turn the ignition on.
2. With the scan tool, select Network View and select Advanced.

NOTE: A red X will be next to the module that is not communicating, indicating that the module is not active on the Bus network. A green check indicates that the module is active on the Bus network.

3. Verify that the TM is active on the bus.

Is the TM active on the bus?

Yes

- Replace and program the Front Control Module.
- Perform the BODY VERIFICATION TEST. Body Verification Test

No

- Go To 4

4. (A922) (A907) FUSED B(+) CIRCUITS OPEN




1. Turn the ignition off.
2. Disconnect the Trailer Lighting Module C2 harness connector.
3. Using a 12-volt test light connected to ground, check the (A922) and (A907) Fused B(+) circuits.

Does the test light illuminate brightly on each circuit?

Yes

- Go To 5

No

- Repair the (A922) or (A907) Fused B(+) circuit for an open or short.
- Perform the BODY VERIFICATION TEST. Body Verification Test

5. (F941) FUSED IGNITION SWITCH OUTPUT (RUN-START) CIRCUIT OPEN




1. Turn the ignition on.
2. Disconnect the Trailer Lighting Module C4 harness connector.
3. Using a 12-volt test light connected to ground, check the (F941) Fused Ignition Switch Output circuit.

Does the test light illuminate brightly?

Yes

- Go To 6

No

- Repair the (F941) Fused Ignition Switch Output circuit for an open or short.
- Perform the BODY VERIFICATION TEST. Body Verification Test

6. (Z923) GROUND CIRCUIT OPEN




1. Using a 12-volt test light connected to 12-volts, check the (Z923) ground circuit.

Does the test light illuminate brightly?

Yes

- Go To 7

No

- Repair the (Z923) ground circuit for an open.
- Perform the BODY VERIFICATION TEST. Body Verification Test

7. (D55) AND (D54) CAN B BUS CIRCUITS OPEN





NOTE: One open circuit will not cause this condition.

1. Measure the voltage between the (D54) CAN B Bus (-) circuit and ground.
2. Measure the voltage between the (D55) CAN B Bus (+) circuit and ground.

Is there any voltage present on either circuit?

Yes

- Replace the Trailer Lighting Module.
- Perform the BODY VERIFICATION TEST. Body Verification Test

No

- Repair the (D55) and (D54) CAN B Bus circuits for an open. Inspect the connector for damage.
- Perform the BODY VERIFICATION TEST. Body Verification Test