Code No.U0121: ABS/ASC CAN timeout <Vehicles with ASC>


caution
  • If diagnosis code No. U0121 is set in the combination meter, always diagnose the CAN bus lines.
  • Whenever the ECU is replaced, ensure that the communication circuit is normal.

JUDGEMENT CRITERIA
With the ignition switch is at "ON" position, diagnosis code No. U1190 is not set and diagnosis code No. U1195 is not set, if the communication with ASC-ECU cannot be established for 2,500 ms or more, the combination meter determines that a problem has occurred.

COMMENTS ON TROUBLE SYMPTOM
The M.U.T.-III shows a diagnosis code status as active.
  • Connector(s) or wiring harness in the CAN bus lines between the combination meter and the ASC-ECU, the power supply circuits to the ASC-ECU itself may be defective.
The M.U.T.-III shows a diagnosis code status as stored.
  • If diagnosis code No. U0121 is set as past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) in the CAN bus lines between the combination meter and the ASC-ECU, or power supply to the ASC-ECU. For diagnosis procedures, refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Treat Past Trouble.
    note For a past trouble, you cannot find it by the M.U.T.-III CAN bus diagnostics even if there is any failure in CAN bus lines. In this case, refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions and check the CAN bus lines. You can narrow down the probable cause of the trouble by referring to the diagnosis code, which is set regarding the CAN communication-linked ECUs (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow).

PROBABLE CAUSES

  • Malfunction of the combination meter
  • Malfunction of the ASC-ECU
  • Malfunction of wiring harness or connector

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics.
Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ). Repair the CAN bus line and go to Step 5.

STEP 2. M.U.T.-III other system diagnosis code.
Check if a diagnosis code, which relates to CAN communication-linked systems below, is set.

    ETACS-ECU

    • Code No. U0121: ABS/ASC CAN timeout

Q. Is the diagnosis code set?
Go to Step 3.
Go to Step 4.

STEP 3. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the combination meter.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)On completion, check whether the diagnosis code is set again.

Q. Is the diagnosis code set?
Replace the ASC-ECU and then go to Step 5.
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 4. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the combination meter.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)On completion, check whether the diagnosis code is set again.

Q. Is the diagnosis code set?
Replace the combination meter. and then go to Step 5.
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. Check whether the diagnosis code is set again.
Recheck if the diagnosis code is set in the combination meter.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)On completion, check whether the diagnosis code is set again.

Q. Is the diagnosis code set?
Return to Step 1.
The procedure is complete.