U0438

U0438-00-IMPLAUSIBLE DATA RECEIVED FROM TRAILER CONTROL MODULE

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

- When Monitored:
Continuously with the ignition on, one valid CAN message received at least once, and no U0002-00-CAN C Bus Off Performance DTC present.

- Set Conditions:
When the Air Suspension Control Module (ASCM) detects an incorrect CAN message from the Integrated Trailer Brake Module (ITBM).





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. VERIFY THE DTC IS ACTIVE

NOTE: This DTC must be active for the results of this test to be valid.

1. Perform any Technical Service Bulletins (TSBs) that may apply.
2. Turn the ignition on.
3. With the scan tool, record and erase the DTCs.
4. Cycle the ignition switch from off to on.
5. With the scan tool, read the DTCs.

Is the DTC active at this time?

Yes

- Go To 2

No

- Perform the ASCM VERIFICATION TEST. ASCM Verification Test.

2. CHECK POWERTRAIN CONTROL MODULE (PCM) CAN BUS DTCS ARE PRESENT
1. With the scan tool, read the PCM DTCs.

Are there any PCM CAN BUS DTCs present?

Yes

- Perform the appropriate diagnostic procedures. Testing and Inspection.
- Perform the ASCM VERIFICATION TEST. ASCM Verification Test.

No

- Go To 3

3. CHECK INTEGRATED TRAILER BRAKE MODULE (ITBM) CAN BUS DTCS ARE PRESENT
1. With the scan tool, read the ITBM DTCs.

Are there any ITBM CAN BUS DTCs present?

Yes

- Perform the appropriate diagnostic procedures. Testing and Inspection.
- Perform the ASCM VERIFICATION TEST. ASCM Verification Test.

No

- Using the schematics as a guide, check the Air Suspension Control Module (ASCM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the Air Suspension Control Module (ASCM). Air Suspension Control Module - Removal.
- Perform the ASCM VERIFICATION TEST. ASCM Verification Test.