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DTC C121C Torque Request Signal Denied
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.
 
 
OPERATION
ASC-ECU sends the signal to the ECM as necessary to decrease the engine output for the ASC system operation.
 
 
 
DTC SET CONDITIONS
This DTC is set when the request for the decrease of output is rejected by the ECM.
 
 
 
PROBABLE CAUSES
  • Wrong coding of ECM
  • ECM malfunction
  • ASC-ECU malfunction
  • External noise interference
 
 
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ."
(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the check result normal?
Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ). On completion, go to Step 2.
 
STEP 2. DTC recheck after resetting CAN bus lines.
Is DTC C121C set?
Go to Step 3.
This diagnosis is complete.
 
STEP 3. Using scan tool (M.U.T.-IIISE), check other system DTC
Use scan tool (M.U.T.-IIISE) to check that the DTC is set in the ECM.
Is the DTC set?
Troubleshoot the ECM DTC (Refer to GROUP 13A - Troubleshooting/Diagnosis function ).
Go to Step 4.
 
STEP 4. Check whether the DTC is set again.
Check that DTC C1707 is set in ASC-ECU.
Is DTC C1707 set?
Troubleshoot for DTC C1707 (Refer to ).
Go to Step 5.
 
STEP 5. Using scan tool (M.U.T.-IIISE), check data list
Check the following data list (Refer to ).
  • Item 13: Allow ESP torque request
Is the check result normal?
Go to Step 6.
Replace the ECM (Refer to GROUP 13A - ECM ).
 
STEP 6. Check whether the DTC is set again.
Erase the DTC.
Is DTC C121C set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ).
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 Use Troubleshooting/How to Cope with Intermittent Malfunctions ).