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Possible Causes

WARNING: This page is about a different car, the 2017 Ford Police Interceptor Utility and 2017 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.
  1. OA1: CHECK FOR ABS MODULE DTCS 
    • Ignition ON, engine OFF.
    • Carry out the ABS self-test.
    • Are there any "lost communication" or "invalid data" DTCs other than U0401:86 present in the ABS module? 
      Yes No
      DIAGNOSE all other ABS module "lost communication" and "invalid data" DTCs before diagnosing DTC U0401:86. REFER to ANTI-LOCK BRAKE SYSTEM (ABS) AND STABILITY CONTROL . Go to  OA2.
  2. OA2: CHECK IF THE ATCM COMMUNICATES ON THE NETWORK 
    • Press the Read Vehicle Information button to view the results of the modules communicating on the network.
    • Retrieve the continuous memory DTCs.
    • Does the ATCM pass the Network Test? 
      Yes No
      Go to  OA3. REFER to COMMUNICATIONS NETWORK to diagnose the ATCM not responding to the scan tool.
  3. OA3: CHECK FOR ATCM DTCS 
    • Carry out the ATCM self-test.
    • Are any DTCs present? 
      Yes No
      REFER to the appropriate Manual Transmission, Clutch and Transfer Case article. Go to  OA4.
  4. OA4: VERIFY ALL WIRING CONNECTIONS ABS) 
    • Ignition OFF.
    • Disconnect the ABS and the BCM C2280A electrical connectors.
    • Disconnect all in-line electrical connectors between the ATCM and the BCM.
    • Using a good light source, inspect all disconnected electrical connectors for the following:
      • corrosion - install new connector or terminal and clean the module pins
      • damaged or bent pins - install new terminals or pins
      • pushed-out pins - install new pins as necessary
      • spread terminals - install new terminals as necessary
    • Are the connectors free of corrosion, damaged pins, bent pins, pushed-out pins and spread terminals? 
      Yes No
      Go to  OA5. REPAIR the affected connectors or terminals. REFER to OEM CONNECTOR REPAIR PROCEDURES for schematic and connector information.
  5. OA5: CHECK FOR CORRECT ATCM OPERATION 
    • Connect all in-line electrical connectors between the ATCM and the BCM. Make sure the connectors seat and latch correctly.
    • Connect the ABS and the BCM C2280A electrical connectors. Make sure the connectors seat and latch correctly.
    • Operate the system and determine if the concern is still present.
    • Is the concern is still present? 
      Yes No
      CHECK OASIS for any applicable TSBs. If a TSB exists for this concern, DISCONTINUE this test and FOLLOW the TSB instructions. If no TSBs address this concern, INSTALL a new ATCM. REFER to the appropriate Manual Transmission, Clutch and Transfer Case article. The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
  6. OA6: CHECK FOR IPC DTCS 
  7. OA7: CHECK THE HILL DESCENT CONTROL SWITCH 
    • Ignition OFF.
    • Press and hold the Hill Descent Control switch while taking the measurement.
    • Measure the resistance between:
      (+) CSS Connector, Component Side (-) CSS Connector, Component Side
      HDC GND
    • Measure the resistance between:
      (+) Hazard Switch Connector, Component Side (-) Hazard Switch Connector, Component Side
      HDC GND
    • Release the Hill Descent Control switch and take another measurement.
    • Measure the resistance between:
      (+) CSS Connector, Component Side (-) CSS Connector, Component Side
      HDC GND
    • Measure the resistance between:
      (+) Hazard Switch Connector, Component Side (-) Hazard Switch Connector, Component Side
      HDC GND
    • Is the resistance less than 3 ohms with the switch pressed and greater than 10, 000 ohms with the switch released? 
      Yes No
      Go to  OA8. INSTALL a new Hazard switch.
      INSTALL a new hazard flasher switch (the hill descent control switch is part of the hazard switch assembly).
      REFER to STOPLAMP SWITCH .
  8. OA8: CHECK THE HILL DESCENT CONTROL SWITCH GROUND CIRCUIT FOR AN OPEN 
    • Measure the resistance between:
      (+) CSS Connector, Harness Side (-)
      GND Ground
    • Measure the resistance between:
      (+) Hazard Switch Connector, Harness Side (-)
      GND Ground
    • Is the resistance less than 3 ohms? 
      Yes No
      Go to  OA9. REPAIR the circuit.
  9. OA9: CHECK THE HILL DESCENT CONTROL SWITCH SIGNAL CIRCUIT FOR AN OPEN 
    • IC connector disconnected.
    • Measure the resistance between:
      (+) CSS Connector, Harness Side (-) IC Connector, Harness Side
      HDC HDC
    • Measure the resistance between:
      (+) Hazard Switch Connector, Harness Side (-) IC Connector, Harness Side
      HDC HDC
    • Is the resistance less than 3 ohms? 
      Yes No
      Go to  OA10. REPAIR the circuit.
  10. OA10: CHECK THE HILL DESCENT CONTROL SWITCH SIGNAL CIRCUIT FOR A SHORT TO GROUND 
    • Measure the resistance between:
      (+) CSS Connector, Harness Side (-)
      HDC Ground
    • Measure the resistance between:
      (+) Hazard Switch Connector, Harness Side (-)
      HDC Ground
    • Is the resistance greater than 10, 000 ohms? 
      Yes No
      Go to  OA11. REPAIR the circuit.
  11. OA11: VERIFY ALL WIRING CONNECTIONS 
    • Ignition OFF.
    • Using a good light source, inspect all disconnected electrical connectors for the following:
      • corrosion - install new connector or terminal and clean the module pins
      • damaged or bent pins - install new terminals or pins
      • pushed-out pins - install new pins as necessary
      • spread terminals - install new terminals as necessary
    • Are the connectors free of corrosion, damaged pins, bent pins, pushed-out pins and spread terminals? 
      Yes No
      Go to  OA12. REPAIR the affected connectors or terminals.
      REFER to OEM CONNECTOR REPAIR PROCEDURES for schematic and connector information.
  12. OA12: CHECK FOR CORRECT IPC OPERATION 
    • IC connector connected. Make sure the connector seats and latches correctly.
    • Operate the system and determine if the concern is still present.
    • Is the concern is still present? 
      Yes No
      INSTALL a new IC.
      CHECK OASIS for any applicable TSBs. If a TSB exists for this concern, DISCONTINUE this test and FOLLOW the TSB instructions. If no TSBs address this concern, INSTALL a new IPC. REFER to INSTRUMENT PANEL CLUSTER (IPC) .
      ORDER a replacement IPC and INCLUDE the RVC form.
      If this is a Ford repair, INCLUDE the RVC on the warranty claim form.      		 The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
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