INSPECTION PROCEDURE 9: ABS operates too frequently.

caution

Whenever ECU is replaced, ensure that the CAN bus lines are normal.

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 may be activated prematurely.
If a non-genuine braking device or non-genuine impact reduction device is mounted, the ABS 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
ABS-ECU malfunction
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

Use M.U.T.-III to check the diagnosis code for the ABS system. (Refer to

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 ABS-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 Disk Check ).
Brake drag force check (Refer to GROUP 35A - Front Disc Brake Assembly or GROUP 35A - Rear Disc Brake Assembly ).

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. M.U.T.-III data list

Check the following data list. (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

Q. Is the check result normal?

	Go to Step 7.

	Go to Step 6.

STEP 6. Wheel speed sensor check

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

<Front> or

<Rear>).

Q. Is the check result normal?

	Go to Step 7.

	Remove the non-genuine electronic device or the wiring harness of non-genuine electronic device. 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

Q. Is the check result normal?

	Go to Step 8.

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

STEP 8. ABS operation check

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).

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

STEP 9. ABS operation check

Q. Is the check result normal?

	This diagnosis is complete.

	Return to Step 1.