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Possible Causes

  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 the ABS module DTC Chart. Go to  OA6.
  2. OA2: VERIFY 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 the Module Communications Network article 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 Four-Wheel Drive Systems or Transfer Case article. Go to  OA4.
  4. OA4: VERIFY ALL WIRING CONNECTIONS ABS) 
    • Ignition OFF.
    • ABS Module connector disconnected. (C135)
    • 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 Connector Repair Procedures Wiring Diagrams for schematic and connector information.
  5. OA5: CHECK FOR CORRECT ATCM OPERATION 
    • ABS Module connector connected. (C135) 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 ATCM.
      CHECK OASIS for any service articles: TSB, GSB (general service bulletin), SSM (special service message) or FSA (Field Service Action).
      If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions.
      If no service articles address this concern, INSTALL a new ATCM. REFER to the appropriate Four-Wheel Drive Systems or 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 

    Carry out the IPC self-test.

    • Are there any DTCs in the IPC? 
      Yes No
      DIAGNOSE all IPC DTCs before diagnosing ABS module DTCs C1000:86 or U0401:86.
      REFER to the Instrumentation, Message Center and Warning Chimes article.      		 Go to  OA7.
  7. OA7: CHECK THE HILL DESCENT CONTROL SWITCH 
    • Ignition OFF.
    • CSS connector disconnected. (C2114)
    • Press and hold the Hill Descent Control switch while taking the measurement.
    • Measure the resistance between:
      (+) CSS (C2114) Connector, Component Side (-) CSS (C2114) Connector, Component Side
      HDC - CET59 (GRAY/VIOLET) - Pin 4 GND - GD214 - Pin 3
    • Measure the resistance between:
      (+) Hazard Switch Connector, Component Side (-) Hazard Switch Connector, Component Side
      HDC GND
    • Measure the resistance between:
      (+) (-)
      HDC GND
    • Release the Hill Descent Control switch and take another measurement.
    • Measure the resistance between:
      (+) CSS (C2114) Connector, Component Side (-) CSS (C2114) Connector, Component Side
      HDC - CET59 (GRAY/VIOLET) - Pin 4 GND - GD214 - Pin 3
    • Measure the resistance between:
      (+) Hazard Switch Connector, Component Side (-) Hazard Switch Connector, Component Side
      HDC GND
    • Measure the resistance between:
      (+) (-)
      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 CSS.
      INSTALL a new CCS (the hill descent control switch is part of the CCS).
  8. OA8: CHECK THE HILL DESCENT CONTROL SWITCH GROUND CIRCUIT FOR AN OPEN 
    • Measure the resistance between:
      (+) CSS (C2114) Connector, Harness Side (-)
      GND - GD214 (BLACK/BLUE) - Pin 3 Ground
    • Measure the resistance between:
      (+) Hazard Switch Connector, Harness Side (-)
      GND Ground
    • Measure the resistance between:
      (+) (-)
      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. (C220)
    • Measure the resistance between:
      (+) CSS (C2114) Connector, Harness Side (-) IC (C220) Connector, Harness Side
      HDC - CET59 (GRAY/VIOLET) - Pin 4 HDC - CET59 - Pin 7
    • Measure the resistance between:
      (+) Hazard Switch Connector, Harness Side (-) IC (C220) Connector, Harness Side
      HDC HDC - CET59 - Pin 7
    • Measure the resistance between:
      (+) (-) IC (C220) Connector, Harness Side
      HDC HDC - CET59 - Pin 7
    • 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 (C2114) Connector, Harness Side (-)
      HDC - CET59 (GRAY/VIOLET) - Pin 4 Ground
    • Measure the resistance between:
      (+) Hazard Switch Connector, Harness Side (-)
      HDC Ground
    • Measure the resistance between:
      (+) (-)
      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 Connector Repair Procedures Wiring Diagrams for schematic and connector information.
  12. OA12: CHECK FOR CORRECT IPC OPERATION 
    • CSS connector connected. (C2114) Make sure the connector seats and latches correctly.
    • IC connector connected. (C220) 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 service articles: TSB, GSB (general service bulletin), SSM (special service message) or FSA (Field Service Action).
      If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions.
      If no service articles address this concern, INSTALL a new IPC. REFER to the Instrumentation, Message Center and Warning Chimes article.
      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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