DTC U0121: F-CAN Malfunction (PCM-ABS Modulator-Control Unit)

WARNING: This page is about a different variant/trim than selected.

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot with the HDS, and review General Troubleshooting Information (see GENERAL TROUBLESHOOTING INFORMATION ).

Clear the DTC with the HDS.
Start the engine, and run it at idle for at least 2 minutes.
Check whether DTC U0121 is indicated in the DTCs/Freeze Data in PGM-FI Mode Menu with the HDS.
Is DTC U0121 indicated in the PGM-FI system?

YES -Troubleshoot DTC U0121 in the PGM-FI system (see DTC U0121: F-CAN MALFUNCTION (ECM/PCM-ABS MODULATOR-CONTROL UNIT) ).

NO -Go to step 4.
Check whether DTC U0121 is indicated in the DTCs/Freeze Data in A/T Mode Menu with the HDS.
Is DTC U0121 indicated?

YES -Go to step 5.

NO -Intermittent failure, the system is OK at this time.
Update the A/T software in the PCM if it does not have the latest software (see ECM/PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE ECM/PCM ).
Check for Pending or Confirmed DTCs with the HDS.
Is DTC U0121 indicated?

YES -If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE ECM/PCM ), then recheck. If the PCM was substituted, go to step 1.

NO -Go to step 7.
Monitor the OBD status for U0121 in the DTCs/Freeze Data in A/T Mode Menu for a pass/fail.
Does the HDS indicate PASSED?

YES -If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM (see ECM/PCM REPLACEMENT ). If any other DTCs were indicated on step 6, go to the indicated DTC's troubleshooting.

NO -Check for poor connections and loose terminals at the PCM. If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE ECM/PCM ), then recheck. If the PCM was substituted, go to step 1. If the HDS indicates NOT COMPLETED, return to step 7 and recheck.