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DTC U0121: ABS/ASC CAN timeout
 
 
caution
  • If DTC No. U0121 is stored, be sure to diagnose the CAN bus line.
  • When replacing the ECU, always check that the communication circuit is normal.
 
 
DIAGNOSTIC FUNCTION
The combination meter stores DTC No.U0121 when it cannot receive signals from the ASC-ECU.
 
 
JUDGMENT CRITERIA
With the ignition switch is at ON position, DTC No. U1190 is not stored and DTC No. U1195 is not stored, if the communication with ASC-ECU cannot be established for 2500 ms or more, the combination meter determines that a problem has occurred.
 
 
TROUBLESHOOTING HINTS
  • The CAN bus line may be defective.
  • The combination meter may be defective.
  • The ASC-ECU may be defective.
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-III), diagnose the CAN bus line
(1)
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).
Connect scan tool (M.U.T.-III). Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(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 CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).
 
STEP 2. Using scan tool (M.U.T.-III), read the ASC diagnostic trouble code
Check if DTC is stored in the ASC-ECU.
Is the DTC stored?
Diagnose the ASC-ECU (Refer to GROUP 35C - Troubleshooting ).
Go to Step 3.
 
STEP 3. Using scan tool (M.U.T.-III), read the ETACS diagnostic trouble code.
Check if DTC No. U0121 is stored in the ETACS-ECU.
Is the DTC stored?
Go to Step 4.
Go to Step 5.
 
STEP 4. Recheck for diagnostic trouble code.
Check again if the DTC is stored in the combination meter.
(1) Erase the DTC.
(2) Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3) On completion, check that the DTC is reset.
Is the DTC stored?
Replace the ASC-ECU and then go to Step 6.
A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the ASC-ECU and the combination meter (Refer to GROUP 00 - How to use troubleshooting/Inspection Service Points ).
 
STEP 5. Recheck for diagnostic trouble code.
Check again if the DTC is stored in the combination meter.
(1) Erase the DTC.
(2) Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3) On completion, check that the DTC is reset.
Is the DTC stored?
Replace the combination meter. and then go to Step 6.
A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the ASC-ECU and the combination meter (Refer to GROUP 00 - How to use troubleshooting/Inspection Service Points ).
 
STEP 6. Recheck for diagnostic trouble code.
Recheck if the DTC is stored in the combination meter.
(1) Erase the DTC.
(2) Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3) On completion, check that the DTC is reset.
Is the DTC stored?
Return to Step 1.
The procedure is complete.