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Pinpoint Test F: Poor Vehicle Tracking During ABS Function

WARNING: This page is about a different car, the 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Vehicle Dynamic Systems for schematic and connector information.

Normal Operation 

Fused battery voltage is provided to the ABS module from battery junction box (BJB) fuses 109 (20A) and 106 (40A) along circuits 483 (RD) and 601 (LB/PK) respectively. Fused ignition voltage is provided from central junction box (CJB) fuse 13 (10A) along circuit 1003 (GY/YE). When necessary, the ABS module supplies voltage to the hydraulic control unit (HCU) assembly and the pump motor is activated. The ABS module is provided a ground along circuit 57 (BK) and the hydraulic pump motor is provided a ground internally through the HCU.

This pinpoint test is intended to diagnose the following:

PINPOINT TEST F: POOR VEHICLE TRACKING DURING ABS FUNCTION 

  1. F1 BLEED THE BRAKE SYSTEM 
    • Bleed the brake system. Refer to BRAKE SYSTEM - GENERAL INFORMATION article.
    • Place the air suspension switch in the ON position and test drive the vehicle.
    • Does the vehicle track poorly? 
    1. YES  : Go to  F2.
    2. NO  : The brake system is operating correctly at this time. TEST the system for normal operation.
  2. F2 CHECK THE LF HCU VALVE OPERATION 
    • With the vehicle in NEUTRAL, position it on a hoist. Refer to JACKING & LIFTING article.
    • Connect the diagnostic tool.
    • Key in ON position.
    • With the wheels off the ground, spin each wheel by hand to make sure that they spin freely (the transmission must be in the NEUTRAL position).
    • Enter the following diagnostic mode on the diagnostic tool: DataLogger ABS: Pump Motor Output Command (PMP_MOTOR)
    • Toggle the PMP_MOTOR output command ON for 4 seconds.
    • Apply moderate brake pedal effort.
    • Have an assistant attempt to rotate the LF wheel.
    • Does the LF wheel rotate? 
    1. YES  : TOGGLE the PMP_MOTOR command OFF. INSTALL a new HCU. REFER to Hydraulic Control Unit (HCU) . TEST the system for normal operation.
    2. NO  : TOGGLE the PMP_MOTOR command OFF. Go to  F3.
  3. F3 CHECK THE LF HCU VALVE RELEASE 
    • Enter the following diagnostic mode on the diagnostic tool: DataLogger ABS: Left Front Inlet Valve and the Left Front Outlet Valve Output Command (LF_INLET and LF_OUTLET)
    • Toggle the LF_INLET and LF_OUTLET output commands ON.
    • Immediately after toggling the output command ON, have an assistant spin the LF wheel using a 2-foot lever, such as a breaker bar.
    • Does the LF wheel spin? 
    1. YES  : TOGGLE both commands OFF. Go to  F4.
    2. NO  : TOGGLE both commands OFF. Go to  F10.
  4. F4 CHECK THE RF HCU VALVE OPERATION 
    • Enter the following diagnostic mode on the diagnostic tool: DataLogger ABS: Pump Motor Output Command (PMP_MOTOR)
    • Toggle the PMP_MOTOR output command ON for 4 seconds.
    • Apply moderate brake pedal effort.
    • Have an assistant attempt to rotate the RF wheel.
    • Does the RF wheel rotate? 
    1. YES  : TOGGLE the PMP_MOTOR command OFF. INSTALL a new HCU. REFER to Hydraulic Control Unit (HCU) . TEST the system for normal operation.
    2. NO  : TOGGLE the PMP_MOTOR command OFF. Go to  F5.
  5. F5 CHECK THE RF HCU VALVE RELEASE 
    • Enter the following diagnostic mode on the diagnostic tool: DataLogger ABS: Right Front Inlet Valve and the Right Front Outlet Valve Output Command (RF_INLET and RF_OUTLET)
    • Toggle the RF_INLET and RF_OUTLET output commands ON.
    • Immediately after toggling the output command ON, have an assistant spin the RF wheel using a 2-foot lever, such as a breaker bar.
    • Does the RF wheel spin? 
    1. YES  : TOGGLE both commands OFF. Go to  F6.
    2. NO  : TOGGLE both commands OFF. Go to  F10.
  6. F6 CHECK THE LR HCU VALVE OPERATION 
    • Enter the following diagnostic mode on the diagnostic tool: DataLogger ABS: Pump Motor Output Command (PMP_MOTOR)
    • Toggle the PMP_MOTOR output command ON for 4 seconds.
    • Apply moderate brake pedal effort.
    • Have an assistant attempt to rotate the LR wheel.
    • Does the LR wheel rotate? 
    1. YES  : TOGGLE the PMP_MOTOR command OFF. INSTALL a new HCU. REFER to Hydraulic Control Unit (HCU) . TEST the system for normal operation.
    2. NO  : TOGGLE the PMP_MOTOR command OFF. Go to  F7.
  7. F7 CHECK THE LR HCU VALVE RELEASE 
    • Enter the following diagnostic mode on the diagnostic tool: DataLogger ABS: Right Front Inlet Valve and the Right Front Outlet Valve Output Command (LR_INLET and LR_OUTLET)
    • Toggle the LR_INLET and LR_OUTLET output commands ON.
    • Immediately after toggling the output command ON, have an assistant spin the LR wheel using a 2-foot lever, such as a breaker bar.
    • Does the LR wheel spin? 
    1. YES  : TOGGLE both commands OFF. Go to  F8.
    2. NO  : TOGGLE both commands OFF. Go to  F10.
  8. F8 CHECK THE RR HCU VALVE OPERATION 
    • Enter the following diagnostic mode on the diagnostic tool: DataLogger ABS: Pump Motor Output Command (PMP_MOTOR)
    • Toggle the ABS module PMP_MOTOR output command ON for 4 seconds.
    • Apply moderate brake pedal effort.
    • Have an assistant attempt to rotate the RR wheel.
    • Does the RR wheel rotate? 
    1. YES  : TOGGLE the PMP_MOTOR command OFF. INSTALL a new HCU. REFER to Hydraulic Control Unit (HCU) . TEST the system for normal operation.
    2. NO  : TOGGLE the PMP_MOTOR command OFF. Go to  F9.
  9. F9 CHECK THE RR HCU VALVE RELEASE 
    • Enter the following diagnostic mode on the diagnostic tool: DataLogger ABS: Right Front Inlet Valve and the Right Front Outlet Valve Output Command (RR_INLET and RR_OUTLET)
    • Toggle the ABS module RR_INLET and RR_OUTLET output commands ON.
    • Immediately after toggling the output command ON, have an assistant spin the RR wheel using a 2-foot lever, such as a breaker bar.
    • Does the RR wheel spin? 
    1. YES  : TOGGLE both commands OFF. The anti-lock brake system is operating correctly at this time. TEST the system for normal operation.
    2. NO  : TOGGLE both commands OFF. Go to  F10.
  10. F10 CHECK FOR DTCs 
    • Retrieve and record any ABS module DTCs.
    • Are any DTCs present? 
    1. YES  : Go to the ABS Module DTC Index .
    2. NO  : INSTALL a new HCU. REFER to Hydraulic Control Unit (HCU) . TEST the system for normal operation.
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