Inspection Procedure 5: Brake Warning Lamp does not Illuminate when the Ignition Switch is Turned to 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, CAN Bus Diagnostics Table ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are 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 break warning lamp to the combination meter through ETACS-ECU via the CAN communication.
  • ASC-ECU illuminates brake warning lamp via ETACS-ECU for approximately 3 seconds for bulb 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
  • Malfunction of the combination meter
  • ASC-ECU malfunction

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 .) Then go to Step 7.

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

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

STEP 3. Actuator test of combination meter
Perform the following actuator test by the combination meter system, and check if the brake warning lamp illuminates. (Refer to GROUP 54A - Combination Meter, Actuator Test Table .)

  • Item No.07: Indicator 1

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 7.

STEP 4. M.U.T.-III other system diagnosis code
Using M.U.T.-III, check that 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 7.
Go to Step 5.

STEP 5. M.U.T.-III other system diagnosis code
Using M.U.T.-III, check that diagnosis code No.U0121 is set by the ETACS system.

Q. Is the diagnosis code set?
Perform troubleshooting on ETACS-ECU. (Refer to GROUP 54A - ETACS, Troubleshooting .) Then go to Step 7.
Go to Step 6.

STEP 6. Retest the system.

Q. Does the brake warning lamp turn ON and OFF
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 7.

STEP 7. Retest the system.

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