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

M1 BLEED THE BRAKE SYSTEM
- Bleed the HCU. Refer to Brake System Bleeding in BRAKE SYSTEM - GENERAL INFORMATION article.
- Test drive the vehicle and verify vehicle tracking during an ABS stop.
- Does the vehicle track correctly during an ABS stop?
- Yes : The brake system is operating correctly. The concern may have been caused by air in the hydraulic system or a sticky valve.
- No : GO to M2.
M2 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 M3.
- No : The condition could be caused by a base brake component or vehicle alignment. REFER to BRAKE SYSTEM - GENERAL INFORMATION article to verify base brake components and REFER to SUSPENSION SYSTEM - GENERAL INFORMATION article to verify suspension components.
M3 CHECK THE ABS INLET VALVE (CLOSE OPERATION)
- Connect the scan tool.
- Ignition ON.
- With the vehicle in NEUTRAL position it on a hoist. Refer to JACKING & LIFTING article.
- Rotate all the wheels to make sure they rotate freely (the transaxle must be in NEUTRAL).
- Apply moderate brake pedal effort.
- Enter the following diagnostic mode on the scan tool: DataLogger - ABS.
- 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 with the brake pedal still applied.
- Does the LF wheel rotate?
- Yes : RELEASE the brake pedal. TOGGLE the LF_INLET active command OFF. GO to M4.
- No : RELEASE the brake pedal. TOGGLE the LF_INLET active command OFF. INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . TEST the system for normal operation.
M4 CHECK THE ABS INLET VALVE (OPEN OPERATION)
- Apply moderate brake pedal effort.
- Have an assistant attempt to rotate the LF wheel.
- Does the LF wheel rotate?
- Yes : RELEASE the brake pedal. INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . TEST the system for normal operation.
- No : RELEASE the brake pedal. GO to M5.
M5 CHECK THE ABS OUTLET VALVE (OPEN OPERATION)
- Apply moderate brake pedal effort.
- Toggle the following active commands ON:
  - Left front inlet valve (LF_INLET)
  - Left front outlet valve (LF_OUTLET)
- At the same time, have an assistant attempt to rotate the LF wheel with the brake pedal still applied.
- Does the LF wheel rotate?
- Yes : RELEASE the brake pedal. TOGGLE all active commands OFF. GO to M6.
- No : RELEASE the brake pedal. TOGGLE all active commands OFF. INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . TEST the system for normal operation.
M6 CHECK THE ABS OUTLET VALVE (CLOSED OPERATION)
- 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 M3) for the RF, LR and RR wheels using the appropriate active commands. If no failure occurs, the system is operating normally.