Pinpoint Test L: Poor Vehicle Tracking During Anti-Lock Function
- L1 BLEED THE BRAKE SYSTEM
- Bleed the brake system using the scan tool. Refer to BRAKE SYSTEM - GENERAL INFORMATION .
- Test drive the vehicle.
- Does the vehicle track correctly?
- Yes: The brake system is operating correctly. The concern may have been caused by air in the hydraulic system or a sticking valve in the HCU.
- No: GO to L2.
- L2 VERIFY VEHICLE TRACKING DURING NON-ABS BRAKING
- Test drive the vehicle and verify vehicle tracking during normal braking.
- Does the vehicle track correctly during normal braking?
- Yes: GO to L3.
- No: The condition could be caused by a base brake component or vehicle alignment. REFER to BRAKE SYSTEM - GENERAL INFORMATION to verify base brake components and REFER to SUSPENSION SYSTEM - GENERAL INFORMATION to verify suspension components.
- L3 CHECK THE ABS INLET VALVE (CLOSED POSITION)
- With the vehicle in NEUTRAL, position it on a hoist. Refer to JACKING & LIFTING .
- Rotate all the wheels to make sure they rotate freely (the transaxle must be in NEUTRAL).
- Connect the scan tool.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: ABS DataLogger.
- Apply moderate brake pedal effort.
- Toggle the left front inlet valve (LF_INLET) active command ON and at the same time, have an assistant attempt to rotate the LF wheel.
- Does the LF wheel rotate?
- Yes: TOGGLE the LF_INLET output command OFF. GO to L4.
- No: TOGGLE the LF_INLET output command OFF. INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . TEST the system for normal operation.
- L4 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 L5.
- L5 CHECK THE ABS OUTPUT VALVE (OPEN POSITION)
- Apply moderate brake pedal effort.
- Toggle the following active commands ON:
- LF_INLET
- Left front outlet valve (LF_OUTLET)
- Hydraulic pump motor (PMP_MOTOR)
- At the same time, have an assistant attempt to rotate the LF wheel.
- Does the LF wheel rotate?
- Yes: TOGGLE all output commands OFF. GO to L6.
- No: TOGGLE all output commands OFF. INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . TEST the system for normal operation.
NOTE: Each activation of the output command runs the pump for 2 seconds. - L6 CHECK THE 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: Beginning with Step L3, REPEAT this procedure for the RF, LR and RR wheels using the appropriate output commands. If no failure occurs, the system is operating normally.