Inspection Procedure 12: ABS/Skid Control/TCL Operates Too Frequently.

Inspection Procedure 12: ABS/skid control/TCL operates too frequently.

CAUTION:
^ If there is any problem in the CAN bus lines, an incorrect diagnostic trouble 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 diagnostic trouble code is detected.
^ If a wheel or tire of other than the genuine specified size is mounted, the ABS/skid control/TCL may be activated prematurely.
^ If non-genuine braking device or non-genuine impact reducing device is mounted, the ABS/skid control/TCL may be activated prematurely.

PROBABLE CAUSES
^ Installation of wheel or tire other than genuine specified size
^ Tire pressure abnormality
^ Tire 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 ASC-ECU)
^ Malfunction of hydraulic circuit
^ External noise interference

DIAGNOSIS

Required Special Tools:
^ MB991958 Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827 M.U.T.-III USB Cable
^ MB991910 M.U.T.-III Main Harness A
^ MB991997: ASC check harness

STEP 1. Check of wheels and tires Perform the following checks.
^ Check of wheel and tire size
^ Tire wear and deterioration
^ Tire pressure check

NOTE: For the tire pressure, refer to the tire pressure label attached to the lower section of driver's side door striker.

Q: Is the check result normal?
YES: Go to Step 2.
NO: Correct the wheels and tires. Then go to Step 9.

STEP 2. Check the DTC.
Using scan tool, check the diagnostic trouble code for ASC system. (Refer to Diagnostic Trouble Code Descriptions.)
Q: Is the check result normal?
YES: Go to Step 3.
NO: Carry out the diagnosis for the DTC. (Refer to Diagnostic Trouble Code Descriptions.) Then go to Step 9.

STEP 3. Check of brake-related components other than hydraulic unit (integrated with ASC-ECU)
Perform the following checks, and also check that no non-genuine parts are installed.
^ Brake pad check
^ Brake disc runout check (Refer to On-vehicle Service, Brake Disc Rotor Check Front Brake Disk Run-Out Check and Correction.)
^ Brake drag force check (Refer to On-vehicle Service, Brake Drag Force Check Brake Drag Force Check.)
Q: Is the check result normal?
YES: Go to Step 4.
NO: 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 On-vehicle Service, Front Wheel Alignment Check and Adjustment Testing and Inspection.)
^ Rear wheel alignment check (Refer to On-vehicle Service, Rear Wheel Alignment Check and Adjustment Rear Suspension.)
Q: Is the check result normal?
YES: Go to Step 5.
NO: 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).
Q: Is the check result normal?
YES: Go to Step 6.
NO: Remove the non-genuine electronic components and wiring harness of non-genuine electronic components. Then go to Step 9.

STEP 6. Scan tool service data
Check the following service data. (Refer to Scan Tool Testing and Procedures.)
^ 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 10: Master cylinder pressure
^ Item 11: Steering angle
^ Item 12: Yaw rate sensor
^ Item 129: FL wheel cylinder pressure
^ Item 130: FR wheel cylinder pressure
^ Item 131: RL wheel cylinder pressure
^ Item 132: RR wheel cylinder pressure
Q: Is the check result normal?
YES: Go to Step 7.
NO (Abnormality of items 01 to 04): Check the installation status of corresponding wheel speed sensor.
NO (Abnormality of items 08, 12): Check the installation status of G and yaw rate sensor.
NO (Abnormality of item 11): Check the installation status of steering wheel sensor.
NO (Abnormality of items 10, 129 to 132): Replace the hydraulic unit (incorporates in ASC-ECU).

STEP 7. Hydraulic unit check
Perform the following actuator tests, and check that the operation is normal. (Refer to Scan Tool Testing and Procedures.)
^ 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?
YES: Go to Step 8.
NO: Replace the hydraulic unit (incorporates in ASC-ECU). Then go to Step 9.

STEP 8. Operation check of ABS/skid control/TCL
Q: Is the check result normal?
YES: Intermittent malfunction.
NO: Replace the hydraulic unit (incorporates in ASC-ECU). Then go to Step 9.

STEP 9. Operation check of ABS/skid control/TCL
Q: Is the check result normal?
YES: The procedure is complete.
NO: Return to Step 1.