Inspection Procedure 8: ASTC OFF indicator lamp stays ON after the engine is started.

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 ASTC-ECU) is replaced, always carry out the calibration of the steering wheel sensor and the G and yaw rate sensor (Refer to ).

OPERATION

ASTC-ECU sends the illumination request signal of the ASTC OFF indicator lamp to the combination meter via the CAN communication.
ASTC-ECU illuminates ASTC OFF indicator lamp for approximately 3 seconds for valve check with the ignition switch turned to the ON position.
When the ASC OFF switch is pressed for three seconds or more, the ASC system will be deactivated.
When the ASC OFF switch is pressed for 15 seconds or more, the ASC system will be held in ON state and it cannot be deactivated until the ignition switch is turned to the ON position the next time.

COMMENTS ON TROUBLE SYMPTOM

This may be caused by faults in the CAN bus line, combination meter or ASTC-ECU.

PROBABLE CAUSES

The CAN bus line is defective.
Malfunction of the combination meter
Malfunction of the hydraulic unit assembly (integrated with ASTC-ECU)

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis

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 .) Then go to Step 8.

STEP 2. M.U.T.-III diagnosis code

Use M.U.T.-III to check the diagnosis code for the ASTC system.

Q. Is the diagnosis code set?

	Carry out the diagnosis for the diagnosis code (Refer to ).

	Go to Step 3.

STEP 3. Measure the resistance at the ASTC-ECU connector

(1)Check the ASTC-ECU connector.

(2)Disconnect the connector and measure at the wiring harness side.

(3)Measure the resistance between SWON terminal and body earth.
OK:

When the ASC OFF switch is pressed: Continuity exists (2 Ω or less)

When the ASC OFF switch is not pressed: No continuity

Q. Is the check result normal?

	Go to Step 6.

	Go to Step 4.

STEP 4. Check the ASC OFF switch

Refer to

Q. Is the check result normal?

	Go to Step 5.

	Replace the ASC OFF switch (Refer to ). Then go to Step 8.

STEP 5. Measure the resistance at the ASC OFF switch connector

(1)Check the ASTC-ECU connector.

(2)Check the ASC OFF switch connector.

(3)Disconnect the connector and measure at the wiring harness side.

(4)Measure the resistance between ASTC-ECU connector SWON terminal and ASC OFF switch and resistance between ASC OFF switch and body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

	Go to Step 6.

	The circuit may be open. Repair the wiring harness wires or connectors between ASTC-ECU connector SWON terminal and ASC OFF switch and resistance between ASC OFF switch and body earth. Then go to Step 8.

STEP 6. M.U.T.-III Diagnosis code of other systems

Use M.U.T.-III to check if the diagnosis code is set in the combination meter system.

Q. Is the diagnosis code set?

	Perform troubleshooting for the combination meter. (Refer to GROUP 54A - Combination Meter, Troubleshooting .) Then go to Step 8.

	Go to Step 7.

STEP 7. Retest the system

Q. Does the ASTC OFF indicator lamp turn ON and OFF normally?

	The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

	Replace the hydraulic unit assembly (integrated with ASTC-ECU) (Refer to ). Then go to Step 8.

STEP 8. Retest the system

Q. Does the ASTC OFF indicator lamp turn ON and OFF normally?

	This diagnosis is complete.

	Return to Step 1.