DTC Troubleshooting

DTC Troubleshooting: U0122

DTC U0122: F-CAN Malfunction (ECM-VSA Modulator-Control Unit)

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information. Initial Inspection and Diagnostic Overview

1. Turn the ignition switch to ON (II).

2. Check for Temporary DTCs or DTCs with the HDS.

Are DTC U0028 and U0122 indicated at the same time?
YES - Go to the troubleshooting for DTC U0028.

NO - Go to step 3.


3. Clear the DTC with the HDS.

4. Check for Temporary DTCs or DTCs with the HDS.

Is DTC U0122 indicated?
YES - Go to step 5.

NO - Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the VSA modulator-control unit and the ECM.


5. Check for communication to the VSA system with the HDS.

Does the HDS communicate with the VSA modulator-control unit?
YES - Go to step 6.

NO - Go to the DLC circuit troubleshooting. Testing and Inspection


6. Turn the ignition switch to LOCK (0).

7. Jump the SCS line with the HDS.

8. Disconnect the VSA modulator-control unit 36P connector. Service and Repair

9. Disconnect ECM connector A (44P).

10. Check for continuity between ECM connector terminal A36 and VSA modulator-control unit 37P connector terminal No. 15.

Is there continuity?
YES - Go to step 11.

NO - Repair open in the wire between the ECM (A36) and the VSA modulator-control unit, then go to step 12.






11. Check for continuity between ECM connector terminal A37 and VSA modulator-control unit 37P connector terminal No. 1.

Is there continuity?
YES - Substitute a known-good VSA modulator-control unit, Service and Repair then go to step 12 and recheck. If DTC U0122 is not indicated, replace the original VSA modulator-control unit, Service and Repair then go to step 12.

NO - Repair open in the wire between the ECM (A37) and the VSA modulator-control unit, then go to step 12.






12. Reconnect all connectors.

13. Turn the ignition switch to ON (II).

14. Reset the ECM with the HDS.

15. Do the ECM idle learn procedure. ECM Idle Learn Procedure

16. Check for Temporary DTCs or DTCs with the HDS.

Is DTC U0122 indicated?
YES - Check for poor connections or loose terminals at the gauge control module (tach), the VSA modulator-control unit, and the ECM, then go to step 1.

NO - Troubleshooting is complete. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.