Pinpoint Test G: Poor Vehicle Tracking During Anti-Lock Function
WARNING: This page is about a different car, the 2005 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
- G1 BLEED THE BRAKE SYSTEM
- Place the air suspension switch in the OFF position.
- Bleed the brake system. Refer to BRAKE SYSTEM-GENERAL INFORMATION .
- Place the air suspension switch in the ON position after the vehicle is off the hoist
- Does the vehicle track poorly?
- Yes : GO to G2.
- No : The brake system is operating correctly at this time. CLEAR the DTCs. REPEAT the self-test.
- G2 CHECK THE LF HYDRAULIC CONTROL UNIT (HCU) VALVE OPERATION
- Enter the following diagnostic mode on the diagnostic tool: Anti-lock Brake System (ABS) Module Active Commands.
- Place the air suspension switch in the OFF position.
- Key in ON position.
- Lift the vehicle and rotate all the wheels to make sure they turn freely (the transmission must be in NEUTRAL).
- Trigger the ABS module active command PMP MOTOR ON for 4 seconds. The trigger must be pushed twice. Each press runs the pump for 2 seconds.
- 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 G3.
- G3 CHECK THE LF HCU VALVE RELEASE
- Trigger the ABS module active command LF INLET ON and LF OUTLET ON.
- Have an assistant turn the LF wheel using a 2-foot lever, such as a breaker bar, immediately after pressing the trigger. The diagnostic tool will energize the valves for only 2 seconds per trigger press.
- Does the LF wheel turn?
- G4 CHECK THE RF HYDRAULIC CONTROL UNIT HCU VALVE OPERATION
- Key in ON position.
- Trigger the ABS module active command PMP MOTOR ON for 4 seconds. The trigger must be pushed twice. Each press runs the pump for 2 seconds.
- Apply moderate brake pedal effort.
- Have an assistant attempt to rotate the RF wheel.
- Does the RF wheel rotate?
- Yes : INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . CLEAR the DTCs. REPEAT the self-test.
- No : GO to G5.
- G5 CHECK THE RF HCU VALVE RELEASE
- Trigger the ABS module active command RF INLET ON and RF OUTLET ON.
- Have an assistant turn the RF wheel using a 2-foot lever, such as a breaker bar, immediately after pressing trigger. The diagnostic tool will energize the valves for only 2 seconds per trigger press.
- Does the RF wheel turn?
- G6 CHECK THE LR HCU VALVE OPERATION
- Key in ON position.
- Trigger the ABS module active command PMP MOTOR ON for 4 seconds. The trigger must be pushed twice. Each press runs the pump for 2 seconds.
- Apply moderate brake pedal effort.
- Have an assistant attempt to rotate the LR wheel.
- Does the LR wheel rotate?
- Yes : INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . CLEAR the DTCs. REPEAT the self-test.
- No : GO to G7.
- G7 CHECK THE LR HCU VALVE RELEASE
- Trigger the ABS module active command LR INLET ON and LR OUTLET ON.
- Have an assistant turn the LR wheel using a 2-foot lever, such as a breaker bar, immediately after pressing trigger. The diagnostic tool will energize the valves for only 2 seconds per trigger press
- Does the LR wheel turn?
- G8 CHECK THE RR HCU VALVE OPERATION
- Key in ON position.
- Trigger the ABS module active command PMP MOTOR ON for 4 seconds. The trigger must be pushed twice. Each press runs the pump for 2 seconds.
- Apply moderate brake pedal effort.
- Have an assistant attempt to rotate the RR wheel.
- Does the RR wheel rotate?
- Yes : INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . CLEAR the DTCs. REPEAT the self-test.
- No : GO to G9.
- G9 CHECK THE RR HCU VALVE RELEASE
- Trigger the ABS module active command RR INLET ON and RR OUTLET ON.
- Have an assistant turn the RR wheel using a 2-foot lever, such as a breaker bar, immediately after pressing trigger. The diagnostic tool will energize the valves for only 2 seconds per trigger press.
- Does the RR Wheel turn?
- Yes : The anti-lock brake system is operating correctly. CLEAR the DTCs. REPEAT the self-test.
- No : GO to B1.
- G10 CHECK FOR DIAGNOSTIC TROUBLE CODES (DTCs)
- Retrieve and document the continuous DTCs.
- Are any DTCs retrieved?
- Yes : GO to the ANTI-LOCK BRAKE SYSTEM (ABS) MODULE DIAGNOSTIC TROUBLE CODE (DTC) INDEX .
- No : INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) . CLEAR the DTCs. REPEAT the self-test.