Pinpoint Test J: Poor Vehicle Tracking During Anti-Lock Function

Test Step 

1. J1 CHECK THE BASE BRAKE SYSTEM
   • Inspect the base brake system.
   • Is the base brake system OK? 

   Result / Action to Take 

   1. Yes:  GO to J2.
   2. No:  REFER to DISC .
2. J2 BLEED THE BRAKE SYSTEM
   • Bleed the brake system. Refer to BLEEDING BRAKE SYSTEM .
   • Check for vehicle tracking poorly.
   • Does the vehicle track poorly? 
   1. Yes:  GO to J3.
   2. No:  The brake system is OK. TEST the system for normal operation.
3. J3 CHECK THE LF ABS VALVE OPERATION
   • Lift the vehicle and rotate all the wheels to make sure they rotate freely (the vehicle must be in neutral).
   NOTE: The trigger must be pressed twice.
   • Each press will run the pump motor for two seconds.
   • Trigger the ABS module active command PMP MOTOR ON for four seconds.
   • Apply moderate brake pedal effort.
   • Have an assistant attempt to rotate the LF wheel while the pump motor is running.
   • Does the LF wheel rotate? 
   1. Yes:  INSTALL a new hydraulic control unit (HCU). REFER to HYDRAULIC CONTROL UNIT . TEST the system for normal operation.
   2. No:  GO to J4.
4. J4 CHECK THE LF ABS VALVE RELEASE
   • Apply moderate brake pedal effort.
   • Trigger the ABS module active command LF INLET and LF OUTLET.
   NOTE: The diagnostic tool will energize the valves for only two seconds per trigger press.
   • Have an assistant rotate the LF wheel immediately after pressing the trigger.
   • Does the LF wheel rotate? 
   1. Yes:  GO to J5.
   2. No:  GO to  J9.
5. J5 CHECK THE RF ABS VALVE OPERATION
   NOTE: Trigger must be pressed twice.
   • Each press will run the pump motor for two seconds.
   • Trigger the ABS module active command PMP MOTOR ON for four seconds.
   • Apply moderate brake pedal effort.
   • Have an assistant attempt to rotate the RF wheel while the pump motor is running.
   • Does the RF wheel rotate? 
   1. Yes:  INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT . TEST the system for normal operation.
   2. No:  GO to J6.
6. J6 CHECK THE RF ABS VALVE RELEASE
   • Apply moderate brake pedal effort.
   • Trigger the ABS module active command RF INLET and RF OUTLET.
   NOTE: The diagnostic tool will energize the valves for only two seconds per trigger press.
   • Have an assistant rotate the RF wheel immediately after pressing trigger.
   • Does the RF wheel rotate? 
   1. Yes:  GO to J7.
   2. No:  GO to  J9.
7. J7 CHECK THE REAR ABS VALVE OPERATION
   NOTE: The trigger must be pressed twice.
   • Each press will run the pump motor for two seconds.
   • Trigger the ABS module active command PMP MOTOR ON for four seconds.
   • Apply moderate brake pedal effort.
   • Have an assistant attempt to rotate the LR and RR wheels while the pump motor is running.
   • Does the LR or RR wheel rotate? 
   1. Yes:  INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT . TEST the system for normal operation.
   2. No:  GO to J8.
8. J8 CHECK THE REAR ABS VALVE RELEASE
   • Apply moderate brake pedal effort.
   • Trigger the ABS module active command R INLET and R OUTLET.
   NOTE: The diagnostic tool will energize the valves for only two seconds per trigger press.
   • Have an assistant rotate the LR and RR wheels immediately after pressing trigger.
   • Does the LR or RR wheel rotate? 
   1. Yes:  The ABS system is operating correctly.
   2. No:  GO to J9.
9. J9 CHECK FOR DTCS
   • Carry out the ABS module self-test.
   • Are any DTCs retrieved? 
   1. Yes:  GO to the ANTI-LOCK BRAKE SYSTEM (ABS) MODULE DIAGNOSTIC TROUBLE CODE (DTC) INDEX .
   2. No:  INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT . TEST the system for normal operation.