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PINPOINT TEST AI : The Trailer Parking Lamps Are Inoperative Or Always On

WARNING: This page is about a different car, the 2016 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

  1. AI1 CHECK FOR VOLTAGE THROUGH THE TRAILER TOW CONNECTOR

    • Ignition OFF.
    • Disconnect: Trailer.
    • Ignition ON.
    • Place the headlamp switch in the PARKLAMPS position.
    • For the 4-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      GFD136999Courtesy of FORD MOTOR COMPANY

      Pin 3
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground
    • For the 7-pin trailer connector, measure:
      Positive Lead Measurement / Action Negative Lead
      GFD137000Courtesy of FORD MOTOR COMPANY

      Pin 6
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground
    • Place the headlamp switch in the OFF position.
    • For the 4-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      GFD136999Courtesy of FORD MOTOR COMPANY

      Pin 3
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground
    • For the 7-pin trailer connector, measure:
      Positive Lead Measurement / Action Negative Lead
      GFD137000Courtesy of FORD MOTOR COMPANY

      Pin 6
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage greater than 11 volts when the headlamps switch in the PARKLAMPS position and 0 volts when the headlamps switch in the OFF position? 

    Yes  The vehicle is operating correctly. SEND the trailer to an authorized camper/trailer repair facility.
    No  If the trailer parking lamps are inoperative, If only equipped with the 4-pin connector, GO to  AI3If the trailer parking lamps are inoperative, If equipped with the 4-pin and 7-pin connectors, GO to  AI2If the trailer parking lamps are always on, GO to  AI6

  2. AI2 CHECK FOR VOLTAGE TO THE TRAILER TOW CONNECTOR (VEHICLE HARNESS)

    • Ignition OFF.
    • Disconnect: Trailer Tow Connector C4099 .
    • Ignition ON.
    • Place the headlamp switch in the PARKLAMPS position.
    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C4099-6
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage greater than 11 volts? 

    Yes  INSTALL a new trailer tow connector.
    No  GO to  AI3

  3. AI3 CHECK THE TRAILER TOW PARKING LAMPS RELAY

    • Ignition OFF.
    • Place the headlamp switch in the OFF position.
    • Disconnect: Trailer Tow Parking Lamps Relay.
    • Substitute with a known good relay.
    • Ignition ON.
    • Place the headlamp switch in the PARKLAMPS position.
    • For the 4-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      GFD136999Courtesy of FORD MOTOR COMPANY

      Pin 3
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground
    • For the 7-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      C4099-6
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage greater than 11 volts? 

    Yes  REMOVE the known good relay. INSTALL a new trailer tow parking lamps relay.
    No  REMOVE the known good relay. GO to  AI4

  4. AI4 CHECK THE TRAILER TOW PARKING LAMPS RELAY VOLTAGE SUPPLY CIRCUITS

    • Place the headlamp switch in the OFF position.
    • Ignition OFF.
    • Disconnect: Trailer Tow Parking Lamps Relay.
    • Ignition ON.
    • Place the headlamp switch in the PARKLAMPS position.
    • Measure:
      Positive Lead Measurement / Action Negative Lead
      GFD137001Courtesy of FORD MOTOR COMPANY

      Trailer Tow Parking Lamps Relay, cavity 1
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground
      GFD137001Courtesy of FORD MOTOR COMPANY

      Trailer Tow Parking Lamps Relay, cavity 3
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground

    Are the voltages greater than 11 volts? 

    Yes  GO to  AI5
    No  VERIFY the BJB fuse 28 (25A) is OK. If OK, REPAIR the circuit in question. If not OK, REFER to the OEM Electrical Wiring Diagram Introduction to identify the possible cause of the circuit short.

  5. AI5 CHECK THE TRAILER TOW PARKING LAMPS RELAY GROUND CIRCUIT

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      GFD137001Courtesy of FORD MOTOR COMPANY

      Trailer Tow Parking Lamps Relay, cavity 1
      GFD134422Courtesy of FORD MOTOR COMPANY
      GFD137001Courtesy of FORD MOTOR COMPANY

      Trailer Tow Parking Lamps Relay, cavity 2

    Are the voltages greater than 11 volts? 

    Yes  REPAIR the parking lamps relay circuit between the parking lamps relay and trailer tow connector.
    No  REPAIR the circuit.

  6. AI6 CHECK THE TRAILER TOW PARKING LAMPS RELAY OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE

    • Ignition OFF.
    • Disconnect: Trailer Tow Parking Lamps Relay.
    • Ignition ON.
    • For the 4-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      GFD136999Courtesy of FORD MOTOR COMPANY

      Pin 3
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground
    • For the 7-pin trailer connector, measure:
      Positive Lead Measurement / Action Negative Lead
      GFD137000Courtesy of FORD MOTOR COMPANY

      Pin 6
      GFD134422Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is any voltage present? 

    Yes  REPAIR the circuit.
    No  INSTALL a new trailer tow parking lamps relay.
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