[Previous][Next]
DTC U0121: ABS/ASC CAN timeout
 
 
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 ).
  • If DTC U0121 is set in electric parking brake ECU, always diagnose the CAN bus line. If there is any fault in the CAN bus lines, an incorrect DTC may be set. In this case, the set DTC is not highly reliable.
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.
 
 
OPERATION
The electric parking brake ECU communicates with the ASC-ECU via the CAN bus lines.
 
 
DTC SET CONDITIONS
If the ECU cannot receive any signal from the ASC-ECU via CAN for 500 ms or more, this DTC will be set.
 
 
TROUBLESHOOTING HINTS
  • The CAN bus line is defective.
  • Power supply circuit for the ASC-ECU fails
  • Malfunction of the ASC-ECU
  • Malfunction of the electric parking brake ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose 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 2.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
 
STEP 2. Using scan tool (M.U.T.-IIISE), check whether the other DTC is set.
Check whether an ASC "time-out" related DTC is set in other ECUs (Refer to GROUP 54C - CAN-Related DTC Table ).
Is the DTC set?
Go to Step 3.
Go to Step 4.
 
STEP 3. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to the LOCK (OFF) position.
(3) Turn the ignition switch to the ON position.
(4) Check the DTC.
Is the DTC U0121 set?
Replace the hydraulic unit assembly (integrated with ASC-ECU) (Refer to GROUP 35C - Hydraulic Unit ).
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
 
STEP 4. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to the LOCK (OFF) position.
(3) Turn the ignition switch to the ON position.
(4) Check the DTC.
Is the DTC U0121 set?
Replace the electric parking brake ECU (Refer to ).
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).