Inspection Procedure 9: ABS/TCL/ASC 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.
  • Whenever the ECU is replaced, ensure that the CAN bus lines are normal.

COMMENTS ON TROUBLE SYMPTOM

  • Although it is difficult to determine the trouble cause since it depends on the running status and road surface condition, a malfunction of hydraulic circuit may be present if no diagnosis code is detected.
  • If a wheel or tyre of other than the genuine specified size is mounted, the ABS/TCL/ASC may be activated prematurely.
  • If non-genuine braking device or non-genuine impact reducing device is mounted, the ABS/TCL/ASC may be activated prematurely.

PROBABLE CAUSES

  • Installation of wheel or tyre other than genuine specified size
  • Tyre pressure abnormality
  • Tyre wear and deterioration
  • Installation of non-genuine braking device or non-genuine impact reducing device
  • Wheel alignment abnormality
  • Malfunction of brake-related components
  • Malfunction of wheel speed sensor
  • Malfunction of G and yaw rate sensor
  • Malfunction of steering wheel sensor
  • Malfunction of hydraulic unit (integrated with TCL/ASC-ECU)
  • Malfunction of hydraulic circuit
  • External noise interference

DIAGNOSIS

STEP 1. Check of wheels and tyres
Perform the following checks.

  • Check of wheel and tyre size
  • Tyre wear and deterioration
  • Tyre pressure check
    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. Then go to Step 9.

STEP 2. Check the diagnosis code.
Using M.U.T.-III, check the diagnosis code for TCL/ASC 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-related components other than hydraulic unit (integrated with TCL/ASC-ECU)
Perform the following checks, and also check that no non-genuine parts are installed.

  • 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 - On-vehicle Service, Brake Drag Force Check .)

Q. Is the check result normal?
Go to Step 4.
Repair or replace the trouble spot. Then go to Step 9.

STEP 4. Wheel alignment check
Perform the following checks, and also check that no non-genuine parts are installed.

  • 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 trouble spot. Then go to Step 9.

STEP 5. Check of wheel speed sensor
Check for the presence of non-genuine electronic components and wiring harness of non-genuine electronic components to near the wheel speed sensor (wheel speed detecting section and wiring harness section). (Refer to .)

Q. Is the check result normal?
Go to Step 6.
Remove the non-genuine electronic components and wiring harness of non-genuine electronic components. Then go to Step 9.

STEP 6. M.U.T.-III service data
Check the following data list. (Refer to .)

  • Item 01: FL wheel speed sensor
  • Item 02: FR wheel speed sensor
  • Item 03: RL wheel speed sensor
  • Item 04: RR wheel speed sensor
  • Item 08: Lateral G sensor
  • Item 11: Steering angle
  • Item 12: Yaw rate sensor

Q. Is the check result normal?
Go to Step 7.
NO (Abnormality of items 01 to 04) : Check the installation status of corresponding wheel speed sensor. (Refer to .)
NO (Abnormality of items 08, 12) : Check the installation status of G and yaw rate sensor. (Refer to .)
NO (Abnormality of item 11) : Check the installation status of steering wheel sensor. (Refer to .)

STEP 7. Hydraulic unit check
Perform the following actuator tests, and check that the operation is normal. (Refer to .)

  • Item 01: FL wheel ABS drive
  • Item 02: FR wheel ABS drive
  • Item 03: RL wheel ABS drive
  • Item 04: RR wheel ABS drive
  • Item 05: FL wheel TCL drive
  • Item 06: FR wheel TCL drive
  • Item 07: RL wheel TCL drive
  • Item 08: RR wheel TCL drive

Q. Is the check result normal?
Go to Step 8.
Replace the hydraulic unit (integrated with TCL/ASC-ECU). (Refer to ). Then go to Step 9.

STEP 8. Operation check of ABS/TCL/ASC

Q. Is the check result normal?
Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)
Replace the hydraulic unit (integrated with TCL/ASC-ECU). (Refer to ). Then go to Step 9.

STEP 9. Operation check of ABS/TCL/ASC

Q. Is the check result normal?
The procedure is complete.
Return to Step 1.