[Previous][Next]
DTC U0121: CAN Time-out Error (ASC)
 
 
 
 
DIAGNOSTIC FUNCTION
The TCM determines that the system is faulty 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 the hydraulic unit (integrated with ASC-ECU)
  • Malfunction of TCM
 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
STEP 1. Using scan tool (M.U.T.-III), diagnose the CAN bus lines.
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Use the scan tool (M.U.T.-III) to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis - CAN Bus Diagnostics Table ).
 
STEP 2. Use scan tool (M.U.T.-III) to check the DTC of other systems.
Check if ASC-related DTC is stored.
Is the ASC-related DTC stored?
Carry out the appropriate troubleshooting (Refer to GROUP 35C, Diagnosis - Diagnostic Trouble Code Chart ).
Go to Step 3.
 
STEP 3. Use scan tool (M.U.T.-III) to check the DTC of other systems.
Is DTC U0121 stored in the other ECU, which communicates with the ASC-ECU via CAN.
Is the DTC stored?
Go to Step 4.
Go to Step 5.
 
STEP 4. Symptom recheck after erasing DTC.
Is the DTC stored?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to GROUP 35C, Hydraulic Unit ).
Intermittent malfunction (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
 
STEP 5. Symptom recheck after erasing DTC.
Is the DTC stored?
Replace the TCM (Refer to ).
Intermittent malfunction (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).