Pinpoint Test J: Poor Vehicle Tracking During Anti-Lock Function
- J1 BLEED THE BRAKE SYSTEM
- Bleed the brake system using the diagnostic tool. Refer to BRAKE SYSTEM BLEEDING .
- Test drive the vehicle.
- Does the vehicle still track poorly?
Yes: GO to J2.
No: The brake system is operating correctly. The concern may have been caused by air in the hydraulic system or a sticky valve.
- J2 CHECK THE ABS INLET VALVE (CLOSED POSITION)
- Connect the scan tool.
- Key in ON position.
- Raise and support the vehicle. Refer to JACKING & LIFTING .
- Rotate all the wheels to make sure they rotate freely (the transaxle must be in NEUTRAL).
- Trigger the ABS module LF INLET ON active command.
- Apply moderate brake pedal effort.
- Have an assistant attempt to rotate the LF wheel.
- Does the LF wheel rotate?
Yes: TRIGGER the LF INLET OFF active command. GO to J3.
No: INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . TEST the system for normal operation.
- J3 CHECK THE ABS INLET VALVE (OPEN POSITION)
- Apply moderate brake pedal effort.
- Have an assistant attempt to rotate the LF wheel.
- Does the LF wheel rotate?
Yes: INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . TEST the system for normal operation.
No: GO to J4.
- J4 CHECK THE ABS OUTPUT VALVE (OPEN POSITION)
- Apply moderate brake pedal effort.
- Trigger ABS module LF INLET ON active command.
- Trigger ABS module ABS POWER ON active command (turns on the pump motor) for 6 seconds. (The trigger must be pressed 3 times. Each press runs the pump for 2 seconds.)
- Trigger the ABS module LF OUTLET ON active command, then trigger the ABS module LF OUTLET OFF active command. Repeat 3 times.
- Have an assistant attempt to rotate the LF wheel.
- Does the LF wheel rotate?
Yes: TRIGGER all active commands OFF. GO to J5.
No: INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . TEST the system for normal operation.
- J5 CHECK ABS INLET AND OUTLET VALVE (CLOSED POSITION)
- Apply moderate brake pedal effort.
- Have an assistant attempt to rotate the LF wheel.
- Does the LF wheel rotate?
Yes: INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . TEST the system for normal operation.
No: REPEAT this procedure (beginning with Step J2) for the RF, LR and RR wheels using the appropriate active commands. If no failure occurs the system is operating normally.