Inspection Procedure 12: ABS/ASC/TCL operates too frequently.

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 G and yaw rate sensor and the steering wheel sensor (Refer to and ).

COMMENTS ON TROUBLE SYMPTOM

Although the cause of the trouble cannot be clearly resolved since it depends on the running status and road surface condition, the malfunction of the hydraulic circuit may occur if any diagnosis code is not detected.
If wheels and tyres other than the ones with genuine specified size are mounted, the ABS/stability control/TCL may be activated prematurely.
If a non-genuine braking device or non-genuine impact reduction device is mounted, the ABS/stability control/TCL may be activated prematurely.

PROBABLE CAUSES

Mounting of wheels and tyres other than with genuine specified size
Tyre pressure abnormality
Tyre wear and deterioration
Mounting of non-genuine braking device or impact reduction device
Wheel alignment abnormality
Malfunction of brake related parts
Malfunction of the wheel speed sensor
Steering wheel sensor malfunction
Malfunction of the hydraulic unit assembly (integrated with ASC-ECU)
Malfunction of hydraulic circuit
External radio wave noise interference

DIAGNOSIS PROCEDURE

STEP 1. Check the wheels and the tyres.

Carry out the following check.

Size check of wheels and tyres.
Tyre wear and deterioration statuses.
Check the tyre pressure.

note For the tyre pressure, refer to the tyre pressure label attached to the lower section of driver’s side door striker.

Q. Is the check result normal?

	Go to Step 2.

	Correct the wheels and tyres in good condition. Then go to Step 9.

STEP 2. Diagnosis code check.

Using M.U.T.-III, check the diagnosis code for the ASC system.

Q. Is the check result normal?

	Go to Step 3.

	Carry out the diagnosis for the diagnosis code (Refer to ). Then go to Step 9.

STEP 3. Check of brake system related components other than hydraulic unit (integrated with ASC-ECU).

At the same time with the following checks, also check that no parts other than the genuine parts are mounted.

Brake pad check. (Refer to GROUP 35A - On-vehicle Service, Brake Pad Check).
Brake disc runout check. (Refer to GROUP 35A - On-vehicle Service, Brake Disc Check).
Brake drag force check. {Refer to GROUP 35A - Front Disc Brake Assembly (front) and GROUP 35A - Rear Drum Brake Assembly (rear)}.

Q. Is the check result normal?

	Go to Step 4.

	Repair or replace the part(s) having damage or other problems. Then go to Step 9.

STEP 4. Wheel alignment check.

At the same time with the following checks, also check that no parts other than the genuine parts are mounted.

Front wheel alignment check (Refer to GROUP 33 - On-vehicle Service, Front Wheel Alignment Check and Adjustment).
Rear wheel alignment check (Refer to GROUP 34 - On-vehicle Service, Rear Wheel Alignment Check and Adjustment).

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the part(s) having damage or other problems. Then go to Step 9.

STEP 5. Wheel speed sensor check.

Check that no non-genuine electronic device or no wiring harness of the device other than genuine electronic device is mounted near the wheel speed sensor (at wheel speed detection section and wiring harness section).

Q. Is the check result normal?

	Go to Step 6.

	Remove the non-genuine electronic device or the wiring harness of non-genuine electronic device. Then go to Step 9.

STEP 6. M.U.T.-III data list.

Check the following service data. (Refer to

Item No. 01: FL wheel speed sensor.
Item No. 02: FR wheel speed sensor.
Item No. 03: RL wheel speed sensor.
Item No. 04: RR wheel speed sensor.
Item No. 06: Lateral G sensor.
Item No. 07: Steering angle.
Item No. 08: Yaw rate sensor.

Q. Is the check result normal?

	Go to Step 7.

	NO (Abnormality with items 01 to 04) : Check the installation status of corresponding wheel speed sensor. Then go to Step 9.

	NO (Abnormality with item No. 06 or 08) : Go to Step 7.

	NO (Abnormality with item No. 07) : Check the installation status of steering wheel sensor (Refer to ). Then go to Step 9.

STEP 7. Hydraulic unit check.

Carry out the following actuator tests, and check if they work normally. (Refer to

Item No.01: FL wheel ABS.
Item No.02: FR wheel ABS.
Item No.03: RL wheel ABS.
Item No.04: RR wheel ABS.
Item No.05: FL wheel TCL.
Item No.06: FR wheel TCL.
Item No.07: RL wheel TCL.
Item No.08: RR wheel TCL.

Q. Is the check result normal?

	Go to Step 8.

	Replace the hydraulic unit assembly (integrated with ASC-ECU) (Refer to ). Then go to Step 9.

STEP 8. ABS/stability control/TCL operation check.

Q. Is the check result normal?

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

	Replace the hydraulic unit assembly (integrated with ASC-ECU) (Refer to ). Then go to Step 9.

STEP 9. ABS/stability control/TCL operation check.

Q. Is the check result normal?

	This diagnosis is complete.

	Return to Step 1.