Inspection Procedure 4: ABS Warning Lamp does not Illuminate when Ignition Switch is Turned to the ON Position (Engine Stopped).


caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C, Trouble code diagnosis ).
  • Before replacing the ECU, ensure that the communication circuit is normal.
  • When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor (Refer to , and ).

OPERATION

  • ASC-ECU sends the illumination request signal of the ABS warning lamp to the combination meter through ETACS-ECU via CAN communication.
  • ASC-ECU illuminates the ABS warning lamp via ETACS-ECU for approximately 3 seconds for valve check with the ignition switch turned to the ON position.

COMMENTS ON TROUBLE SYMPTOM
This may be caused by faults in the CAN bus line, ETACS-ECU, combination meter or ASC-ECU.

PROBABLE CAUSES

  • Damaged wiring harness and connectors
  • Malfunction of ETACS-ECU
  • Combination meter malfunction
  • ASC-ECU malfunction
  • Malfunction of coding data for ETACS-ECU

DIAGNOSIS PROCEDURE

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

Q. Is the check result normal?
Go to Step 2.
Repair the CAN bus lines. (Refer to GROUP 54C - CAN Bus Diagnostic table .)

STEP 2. M.U.T.-III diagnosis code
Use M.U.T.-III to check the diagnosis code for the ASC system. (Refer to .)

Q. Is the diagnosis code set?
Carry out the diagnosis for the diagnosis code. (Refer to .)
Go to Step 3.

STEP 3. Actuator test
Perform the actuator test No. 07 of the combination meter system, and check if the ABS warning lamp illuminates. (Refer to GROUP 54A - Combination Meter, Actuator Test Table .)

Q. Is the check result normal?
Go to Step 4.
Diagnose the combination meter. (Refer to GROUP 54A - Combination Meter, Trouble Symptom Chart .) Then go to Step 8.

STEP 4. ETACS-ECU coding data check
Use M.U.T.-III to check if coding data stored in ETACS-ECU is normal. (Refer to GROUP 00 - Coding List .)

Q. Is the check result normal?
Go to Step 5.
Replace the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU ), and then go to Step 8.

STEP 5. M.U.T.-III diagnosis code for other systems
Using M.U.T.-III, check that the diagnosis code No.U0141 is set by the combination meter system.

Q. Is the diagnosis code set?
Diagnose the combination meter. (Refer to GROUP 54A - Combination Meter, Troubleshooting .) Then go to Step 8.
Go to Step 6.

STEP 6. M.U.T.-III diagnosis code for other systems
Using M.U.T.-III, check that the diagnosis code No.U0121 is set by the ETACS system.

Q. Is the diagnosis code set?
Troubleshoot the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU, Troubleshooting ), and then go to Step 8.
Go to Step 7.

STEP 7. Retest the system.

Q. Does the ABS warning lamp turn ON and OFF normally?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)
Replace the hydraulic unit (ASC-ECU) (Refer to ), and then go to Step 8.

STEP 8. Retest the system.

Q. Does the ABS warning lamp turn ON and OFF normally?
This diagnosis is complete.
Return to Step 1.