Code No. U0121: ABS/ASC-ECU Time Out



DIAGNOSIS CODE SET CONDITIONS
  • Open circuit or short circuit occurs in the CAN communication line (CAN_H, CAN_L).
  • Reception from ABS/ASC-ECU becomes impossible for a specified time or more.

PROBABLE CAUSES



  • Damaged harness or connector
  • Malfunction of the CAN communication
  • Malfunction of the ABS/ASC-ECU
  • Malfunction of the A/T-ECU

DIAGNOSIS PROCEDURE


STEP 1. Check the CAN communication system malfunction.



  • Check that the CAN system-related diagnosis code other than U0121 is set.

  • Check if the CAN-related diagnosis code is set with ABS/ASC-ECU.

  • Check if the failure related to the ABS/ASC occurs.

Q. Is the check result normal?

Go to Step 2.
Repair or replace the failure section.

STEP 2. Check the CAN communication lines.


[C-138 A/T-ECU connector (vehicle side, disconnected)]
Between C-138 terminal No. 10, 11 and the CAN communication lines of ABS/ASC-ECU: Continuity exists.
When the continuity check result is OK, check that the wiring harness is not shorted to the body and other wiring harness. Also, check for a short circuit between the twisted pair cables.

Q. Is the check result normal?

Go to Step 3.
Repair or replace the failure section.

STEP 3. Check the ABS/ASC-ECU, the A/T-ECU connector pin terminal, and the connection status.


Q. Is the check result normal?

Repair or replace the failure section.
Replace the A/T-ECU.