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DTC U0121: CAN Time-out Error (ASC)
 
 
 
 
DIAGNOSTIC FUNCTION
The TCM determines that the system is defective if the ECU can receive no CAN communication information from the ASC-ECU.
 
 
JUDGMENT CRITERIA
No information is received from the ASC-ECU for 2.5 seconds.
 
 
PROBABLE CAUSES
  • Malfunction of the CAN bus line
  • Malfunction of ASC-ECU
  • Malfunction of TCM
 
 
DIAGNOSIS
STEP 1. M.U.T.-III CAN bus diagnostics
Use M.U.T.-III to perform the CAN bus diagnosis.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting, Diagnostic Trouble Code Chart ).
 
STEP 2. M.U.T.-III diagnostic trouble code
Check if the ASC-related diagnostic trouble code is stored.
Is the ASC-related diagnostic trouble code stored?
Carry out the appropriate troubleshooting.
Go to Step 3.
 
STEP 3. M.U.T.-III diagnostic trouble code
Is diagnostic trouble code No. U0121 stored in the other ECU, which communicates with the ASC-ECU via CAN?
Is the diagnostic trouble code stored?
Go to Step 4.
Go to Step 5.
 
STEP 4. Symptom recheck after erasing diagnostic trouble code
Is the diagnostic trouble code stored?
Replace ASC-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions .).
 
STEP 5. Symptom recheck after erasing diagnostic trouble code
Is the diagnostic trouble code stored?
Replace TCM.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions .).