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

1. 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? 

     1. YES:  Go to Step 2.
     2. NO:  Correct the wheels and tires. Then go to Step  9.
2. STEP 2. Check the DTC. 

   Using scan tool, check the diagnostic trouble code for ASC system. (Refer to DIAGNOSTIC TROUBLE CODE CHART  .)

   Q: Is the check result normal? 

   1. YES:  Go to Step 3.
   2. NO:  Carry out the diagnosis for the DTC. (Refer to DIAGNOSTIC TROUBLE CODE CHART  .) Then go to Step  9.
3. 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 (Refer to BRAKE PAD CHECK .)
   • Brake disc runout check (Refer to BRAKE DISC ROTOR CHECK .)
   • Brake drag force check (Refer to BRAKE DRAG FORCE CHECK .)

   Q: Is the check result normal? 

   1. YES:  Go to Step 4.
   2. NO:  Repair or replace the trouble spot. Then go to Step  9.
4. 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 FRONT WHEEL ALIGNMENT CHECK AND ADJUSTMENT .)
   • Rear wheel alignment check (Refer to REAR WHEEL ALIGNMENT CHECK AND ADJUSTMENT .)

   Q: Is the check result normal? 

   1. YES:  Go to Step 5.
   2. NO:  Repair or replace the trouble spot. Then go to Step  9.
5. 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 WHEEL SPEED SENSOR  .)

   Q: Is the check result normal? 

   1. YES:  Go to Step 6.
   2. NO:  Remove the non-genuine electronic components and wiring harness of non-genuine electronic components. Then go to Step  9.
6. STEP 6. Scan tool service data 

   Check the following service data. (Refer to DATA LIST REFERENCE TABLE  .)

   • 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? 

   1. YES:  Go to Step 7.
   2. NO (Abnormality of items 01 to 04)  : Check the installation status of corresponding wheel speed sensor. (Refer to WHEEL SPEED SENSOR  .)
   3. NO (Abnormality of items 08, 12)  : Check the installation status of G and yaw rate sensor. (Refer to G AND YAW RATE SENSOR  .)
   4. NO (Abnormality of item 11)  : Check the installation status of steering wheel sensor. (Refer to STEERING WHEEL SENSOR  .)
   5. NO (Abnormality of items 10, 129 to 132):  Replace the hydraulic unit (integrated with ASC-ECU). (Refer to HYDRAULIC UNIT  .)
7. STEP 7. Hydraulic unit check 

   Perform the following actuator tests, and check that the operation is normal. (Refer to DATA LIST REFERENCE TABLE  .)

   • 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? 

   1. YES:  Go to Step 8.
   2. NO:  Replace the hydraulic unit (integrated with ASC-ECU). (Refer to HYDRAULIC UNIT  .) Then go to Step  9.
8. STEP 8. Operation check of ABS/skid control/TCL 

   Q: Is the check result normal? 

   1. YES:  Intermittent malfunction. (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .)
   2. NO:  Replace the hydraulic unit (integrated with ASC-ECU). (Refer to HYDRAULIC UNIT  .) Then go to Step 9.
9. STEP 9. Operation check of ABS/skid control/TCL 

   Q: Is the check result normal? 

   1. YES:  The procedure is complete.
   2. NO:  Return to Step  1.