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Home >> Ford >> 2020 >> Explorer ST >> Repair and Diagnosis >> Brakes >> Brakes Control Systems >> Abs Guided Routine >> Pinpoint Tests >> Pinpoint Tests CT: ABS Module DTC C1A99 - Pressure Sensor >> Possible Causes
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Possible Causes

  1. CT1: RECHECK FOR ABS MODULE DTC C1A99 
    • Ignition ON, engine OFF.

      Carry out the ABS self-test.

    • Is DTC C1A99:xx currently present and active in the ABS module? 
      Yes No
      Go to  CT2. GATHER information from the customer about conditions necessary to duplicate the concern.
      Some things to ask the customer may include; how often, drive time, down time, climate conditions (inside and outside the vehicle), speed traveling or maneuvering performed when the fault occurs.
      OPERATE the vehicle in the conditions outlined by the customer and MONITOR the PCM BOO1 and BOO2 PIDs, and the ABS module Hydraulic pressure PIDs to determine a focus area.
      If there is pressure above 1, 379 kPa (200 PSI) and no BOO reading, an incorrectly installed stoplamp switch is the most likely cause.
  2. CT2: CHECK THE ABS MODULE HYDRAULIC PRESSURE PID 
    NOTE: The brake pressure PID should read close to 0 kPa (0 PSI) with the brake pedal released and increase when applying the brake pedal.
    • Access the ABS and monitor the BRKHYDPRESS (PRESS) PID.
    • While monitoring the PID, fully apply the brake pedal.
    • Does the PID read close to 0 kPa (0 PSI) without the brake pedal applied and increase when the pedal is pressed? 
      Yes No
      Go to  CT4. Go to  CT3.
  3. CT3: CHECK FOR BRAKE DRAG 
    • With the transmission in NEUTRAL, position the vehicle on a hoist. Refer to Jacking and Lifting article
    • Spin each wheel by hand and check for any indication of brake drag.
    • Do all 4 wheels spin freely with little to no resistance? 
      Yes No
      Go to  CT4. DIAGNOSE and REPAIR the brake drag concern.
      REFER to the Brake System General Information article.
  4. CT4: CHECK THE PCM BOO1 AND BOO2 PIDS 
    • Ignition ON, engine OFF.
    • Monitor the following PIDs while pressing and releasing the brake pedal.
    • Access the PCM and monitor the BOO1 (MODE) PID.
    • Access the PCM and monitor the BOO2 (MODE) PID.
    • Do the PIDs indicate ON with the brake pedal applied and OFF with the brake pedal released? 
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