Code No. C121C Torque request signal rejection


caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C, Trouble code diagnosis ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION
ASC-ECU sends the signal to the engine ECU as necessary to decrease the engine output for the ASC system operation.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set when the request for the decrease of output is rejected by the engine ECU.

PROBABLE CAUSES

  • Wrong coding
  • Engine ECU malfunction
  • ASC-ECU malfunction
  • External noise interference

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis
Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting ). On completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines

Q. Is the diagnosis code No. C121C set?
Go to Step 5.
This diagnosis is complete.

STEP 3. M.U.T.-III other system diagnosis code
Use M.U.T.-III to check that the diagnosis code is set in the engine ECU.

Q. Is the diagnosis code set?
Troubleshoot the engine ECU diagnosis code (Refer to GROUP 13A - Troubleshooting ).
Go to Step 4.

STEP 4. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. C121C set?
Replace the ASC-ECU.
If the trouble symptom is resolved, an intermittent malfunction such as poorly engaged connector(s) or wiring harness is suspected (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 5. M.U.T.-III diagnosis code
Check that the diagnosis code No. U1417 is set in ASC-ECU.

Q. Is the diagnosis code No. U1417 set?
Troubleshoot for the diagnosis code No. U1417. Refer to .
Replace the ASC-ECU.