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Pinpoint Test D : The Trailer Parking Lamps Are Inoperative Or Always On

WARNING: This page is about a different car, the 2015 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

  1. D1 CHECK FOR VOLTAGE THROUGH THE TRAILER TOW CONNECTOR

    • Ignition OFF.
    • Disconnect: Trailer.
    • Ignition ON.
    • Place the headlamp switch in the PARKING LAMPS position.
    • If equipped with a 4-pin connector only, measure:
      Positive Lead Measurement / Action Negative Lead
      C4098-3
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground
    • If equipped with a 4-pin and 7-pin connector, for 4-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      4-Pin Connector, Pin 3
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground
    • If equipped with a 4-pin and 7-pin connector, for 7-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      7-Pin Connector, Pin 6
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground
    • Place the headlamp switch in the OFF position.
    • If equipped with a 4-pin connector only, measure:
      Positive Lead Measurement / Action Negative Lead
      C4098-3
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground
    • If equipped with a 4-pin and 7-pin connector, for 4-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      4-Pin Connector, Pin 3
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground
    • If equipped with a 4-pin and 7-pin connector, for 7-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      7-Pin Connector, Pin 6
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage greater than 11 volts when the headlamps switch in the PARKING LAMPS 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 equipped with a 4-pin connector only, If the trailer parking lamps are inoperative, GO to  D3 If equipped with a 4-pin and 7-pin connector, If the trailer parking lamps are inoperative, GO to  D2 If the trailer parking lamps are always on, GO to  D8

  2. D2 CHECK FOR VOLTAGE TO THE TRAILER TOW CONNECTOR (VEHICLE HARNESS)

    • Ignition OFF.
    • Disconnect: Trailer Tow C4099 .
    • Ignition ON.
    • Place the headlamp switch in the PARKING LAMPS position.
    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C4099-6
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage greater than 11 volts? 

    Yes  INSTALL a new trailer tow connector. TEST the system for normal operation.
    No  GO to  D3

  3. D3 CHECK THE TRAILER TOW PARKING LAMPS RELAY

    • Place the headlamp switch in the OFF position.
    • Ignition OFF.
    • Disconnect: Trailer Tow Parking Lamps Relay.
    • Substitute with a known good relay.
    • Ignition ON.
    • Place the headlamp switch in the PARKING LAMPS position.
    • If equipped with a 4-pin connector only, measure:
      Positive Lead Measurement / Action Negative Lead
      C4098-3
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground
    • If equipped with a 4-pin and 7-pin connector, measure:
      Positive Lead Measurement / Action Negative Lead
      C4099-6
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage greater than 11 volts? 

    Yes  REMOVE the known good relay. INSTALL a new trailer tow parking lamp relay. TEST the system for normal operation.
    No  REMOVE the known good relay. GO to  D4

  4. D4 CHECK THE TRAILER TOW PARKING LAMPS RELAY VOLTAGE SUPPLY CIRCUITS

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      Trailer Tow Parking Lamps Relay Socket Pin 1
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground
      Positive Lead Measurement / Action Negative Lead
      Trailer Tow Parking Lamps Relay Socket Pin 3
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage greater than 11 volts? 

    Yes  GO to  D5
    No  VERIFY the BJB fuse 34 (25A) are OK. If OK, REPAIR the circuit in question. If not OK, REFER to the OEM WIRING DIAGRAMS to identify the possible cause of the circuit short.

  5. D5 CHECK THE TRAILER TOW PARKING LAMPS RELAY GROUND

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      Trailer Tow Parking Lamps Relay Socket Pin 1
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Trailer Tow Parking Lamps Relay Socket Pin 2

    Is the voltage greater than 11 volts? 

    Yes  REPAIR the parking lamps relay output circuit between the parking lamps relay and trailer tow connector.
    No  GO to  D6

  6. D6 CHECK THE TRAILER TOW PARKING LAMPS RELAY CONTROLLED GROUND CIRCUIT FOR A SHORT TO VOLTAGE

    • Ignition OFF.
    • Place the headlamp switch in the OFF position.
    • Ignition ON.
    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C2280F-12
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is any voltage present? 

    Yes  REPAIR the circuit.
    No  GO to  D7

  7. D7 CHECK THE TRAILER TOW PARKING LAMPS RELAY CONTROLLED GROUND CIRCUIT FOR AN OPEN

    • Ignition OFF.
    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C2280F-12
      GFD38391Courtesy of FORD MOTOR COMPANY
      		 Trailer Tow Parking Lamps Relay Socket Pin 2

    Is the resistance less than 3 ohms? 

    Yes  GO to  D10
    No  REPAIR the circuit.

  8. D8 CHECK THE TRAILER TOW PARKING LAMPS RELAY OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE

    • Place the headlamp switch in the OFF position.
    • Ignition OFF.
    • Disconnect: Trailer Tow Parking Lamps Relay.
    • Disconnect: If equipped, TRM C2498C .
    • Ignition ON.
    • Measure:
      Positive Lead Measurement / Action Negative Lead
      Trailer Tow Parking Lamps Relay Socket Pin 5
      GFD38392Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is any voltage present? 

    Yes  REPAIR the circuit.
    No  GO to  D9

  9. D9 CHECK THE TRAILER TOW PARKING LAMPS RELAY GROUND CIRCUIT FOR A SHORT TO GROUND

    • Ignition OFF.
    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C2280F-12
      GFD38391Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance greater than 10, 000 ohms? 

    Yes  GO to  D10
    No  REPAIR the circuit.

  10. D10 CHECK FOR CORRECT BCM (BODY CONTROL MODULE) OPERATION

    • Disconnect and inspect all BCM connectors.
    • Repair:
      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins
      • pushed-out pins - install new pins as necessary
    • Reconnect the BCM connectors. Make sure they seat and latch correctly.
    • Operate the system and determine if the concern is still present.

    Is the concern still present? 

    Yes  CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, Refer to BCM Hardware Testing .
    No  The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.
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