Inspection Procedure 7: ABS 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.

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 suspension 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 suspension
Wheel alignment abnormality
Malfunction of brake related parts
Malfunction of the wheel speed sensor
Malfunction of the hydraulic unit assembly (integrated with ABS-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 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 assembly (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 .)
Brake disc runout check (Refer to .)
Brake drag force check (Refer to (front) and (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 <2WD (except High rider)>, <2WD (High rider), 4WD>].

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). (Refer to

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 12: FL wheel speed sensor
Item 13: FR wheel speed sensor
Item 14: RL wheel speed sensor
Item 15: RR wheel speed sensor

Q. Is the check result normal?

	Go to Step 7.

	NO (Abnormality with items 12 to 15) : Check the installation status of corresponding wheel speed sensor. (Refer to .)

	NO (Abnormality with item 20) : Go to Step 7.

	NO (Abnormality with item 21) : Check the installation status of steering wheel sensor. (Refer to .)

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 assembly (integrated with ABS-ECU) (Refer to ). Then go to Step 9.

STEP 8. ABS 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 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.