U0121

DTC U0121: F-CAN Malfunction (TCS-ECM/PCM)

NOTE: If DTC U0073 is stored at the same time as DTC U0121, troubleshoot DTC U0073 first, then recheck for DTC U0121.

1. Turn the ignition switch ON (II).
2. Clear the DTC with the HDS.
3. Check for Temporary DTCs or DTCs with the HDS.

Is DTC U0121 indicated?

YES - Go to step 4.

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the gauge assembly, the ABS/TCS control unit, and the ECM/PCM.

4. Check for a DTC in the DTCs MENU with the HDS.

Is TCS DTC 86 indicated?

YES - Go to step 5.

NO - Go to step 9.

5. Turn the ignition switch OFF.
6. Disconnect the ABS/TCS control unit 47P connector.




7. Check for continuity between ABS/TCS control unit 47P connector terminals No.14 and No.30.

Is there continuity?

YES - Go to step 8.

NO - Repair open in the wire between the ABS/TCS control unit (No.14, No.30) and the ECM/PCM (A15, A26),then go to step 14.

8. Check for a poor connection at the cabin wire harness/dashboard wire harness 20P connector.

Is the connection OK?

YES - Substitute a known-good ABS/TCS control unit, then go to step 14 and recheck. If no DTCs are indicated, replace the original ABS/TCS control unit, then go to step 14.

NO - Repair the poor connection then go to step 14.

9. Turn the ignition switch OFF.
10. Disconnect the ABS/TCS control unit 47P connector
11. Turn the ignition switch ON (II).




12. Measure voltage between ABS/TCS control unit 47P connector terminal No.38 and body ground.

Is there battery voltage?

YES - Go to step 13.

NO - Check the No.21 IG METER (7.5 A) fuse in the under-dash fuse/relay box. If the fuse is OK, repair open in the wire between the No.21 IG METER (7.5 A) fuse and the ABS/TCS control unit, then go to step 14.




13. Check for continuity between ABS/TCS control unit 47P connector terminal No.32 and body ground.

Is there continuity?

YES - Substitute a known-good ABS/TCS control unit, then go to step 14 and recheck. If no DTCs are indicated, replace the original ABS/TCS control unit, then go to step 14.

NO - Repair open in the wire between the ABS/TCS control unit and G203, then go to step 14.

14. Turn the ignition switch ON (II).
15. Reset the ECM/PCM with the HDS.
16. Do the ECM/PCM idle learn procedure.
17. Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?

YES - If DTC U0121 is indicated, check for poor connections or loose terminals at the gauge assembly, the ABS/TCS control unit, and the ECM/PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.

NO - Troubleshooting is complete.