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.

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 Diagnostics 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. M.U.T.-III Special Function for other system

Perform the following special function by the combination meter system, and check if the ABS warning lamp illuminates (Refer to GROUP 54A - Combination Meter

Item 6: Indicator (AUTO)

Q. Is the check result normal?

	Go to Step 4

	Replace the combination meter.

STEP 4. M.U.T.-III other system diagnosis code

Using M.U.T.-III, check that diagnosis code No.U0141 is not set by the combination meter system.

Q. Is the diagnosis code set?

	Diagnose the combination meter (Refer to GROUP 54A - Combination Meter/Diagnosis Code ). 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 not set by the ETACS system.

Q. Is the diagnosis code set?

	Perform troubleshooting on ETACS-ECU (Refer to GROUP 54A - ETACS/Diagnosis Code ). 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 Use Troubleshooting/How to Cope with Intermittent Malfunctions ).

	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.