Inspection Procedure 13: 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

1. STEP 1. Check the wheels and the tires. 

   Carry out the following check.

   • Size check of wheels and tires
   • Tire wear and deterioration status
   • Check the tire pressure.
     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 in good condition. Then go to  Step 9.
2. STEP 2. Diagnostic trouble code check 

   Use scan tool MB991958 to check the diagnostic trouble code for the 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 diagnostic trouble code. (Refer to DIAGNOSTIC TROUBLE CODE CHART  .) Then go to  Step 9.
3. 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 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 part(s) having damage or other problems. Then go to  Step 9.
4. 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 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 part(s) having damage or other problems. Then go to  Step 9.
5. STEP 5. 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 REMOVAL SERVICE POINT  ).

   Q: Is the check result normal? 

   1. YES:  Go to Step 6.
   2. NO:  Remove the non-genuine electronic device or the wiring harness of non-genuine electronic device. Then go to  Step 9.
6. STEP 6. M.U.T.-III data list 

   Check the following data list (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 11: Steering angle sensor
   • Item 12: Yaw rate sensor

   Q: Is the check result normal? 

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

   Carry out the following actuator tests, and check if they work normally (Refer to ACTUATOR TEST REFERENCE TABLE  ).

   • Item No. 01: FL wheel ABS
   • Item No. 02: FR wheel ABS
   • Item No. 03: RL wheel ABS
   • Item No. 04: RR wheel ABS
   • Item No. 05: FL wheel TCL
   • Item No. 06: FR wheel TCL
   • Item No. 07: RL wheel TCL
   • Item No. 08: RR wheel TCL

   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. ABS/skid control/TCL operation check 

   Q: Is the check result normal? 

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

   Q: Is the check result normal? 

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