Diagnostic Test
- CHECK FOR DTC U0401-IMPLAUSIBLE DATA RECEIVED FROM ECM/PCM NOTE: This DTC must be active for the results of this test to be valid.
- Ignition on, engine not running.
- With the scan tool, record and erase DTCs.
- Cycle the ignition switch from off to on.
- With the scan tool, read DTCs.
Does the scan tool display: U0401-IMPLAUSIBLE DATA RECEIVED FROM ECM/PCM?
Yes
- Go to 2
No
- Refer to Non-DTC Diagnostics/Communication - Diagnosis and Testing and perform the Lost Stored Communication DTC diagnostic procedure.
- CHECK IF FCM CAN BUS DTCS ARE PRESENT
- With the scan tool, read FCM DTCs.
Are there any FCM CAN BUS DTCs present?
Yes
- Perform the appropriate diagnostic procedure. Refer to DTC-Based Diagnostics/MODULE, Front Control (FCM) - Diagnosis and Testing .
No
- Go to 3
- With the scan tool, read FCM DTCs.
- CHECK IF ENGINE DTCS ARE PRESENT
- With the scan tool, read Powertrain Control Module DTCs.
Are there any Powertrain Control Module DTCs present?
Yes
- Perform the appropriate diagnostic procedure. Refer to DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Diagnosis and Testing .
No
- Using the schematics as a guide, check the Final Drive Control Module (FDCM) pins, terminals, and wiring harness connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the Final Drive Control Module (FDCM) in accordance with the Service Information.
- Perform the TRANSFER CASE VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Final Drive Control (FDCM) - Standard Procedure .
- With the scan tool, read Powertrain Control Module DTCs.