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Pinpoint Test Ab : The TRM (Trailer Module) Does Not Respond To The Diagnostic Scan Tool

WARNING: This page is about a different car, the 2019 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.
  1. Refer to OEM WIRING DIAGRAMS FOR MODULE COMMUNICATIONS NETWORK - CELL 14 for schematic and connector information. Refer to OEM WIRING DIAGRAM FOR TRAILER/CAMPER ADAPTER - CELL 95 for schematic and connector information.

    Normal Operation and Fault Conditions 

    The TRM communicates on the MS-CAN.

    Possible Sources 

    • Fuse
    • Wiring, terminals and connector
    • TRM

    Visual Inspection and Pre-checks 

    • Verify BJB fuse 78 (40A) is OK.

  2. AB1 CHECK THE TRM (TRAILER MODULE) VOLTAGE SUPPLY CIRCUIT FOR AN OPEN

    • Ignition OFF.

    • Disconnect: TRM C425A.

    • Ignition ON.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C425A-1
      GFD385083Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage greater than 11 volts? 

    Yes  GO to  AB2
    No  VERIFY BJB fuse 78 (40A) is OK. If OK, REPAIR the circuit. If not OK, REFER to the Wiring Diagrams service information to identify the possible causes of the circuit short.

  3. AB2 CHECK THE TRM (TRAILER MODULE) GROUND CIRCUIT FOR AN OPEN

    • Ignition OFF.

    • Disconnect: TRM C425B.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C425B-1
      GFD385385Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance less than 3 ohms? 

    Yes  GO to  AB3
    No  REPAIR the circuit.

  4. AB3 CHECK THE MS-CAN (MEDIUM SPEED-CONTROLLER AREA NETWORK) CIRCUITS BETWEEN THE TRM (TRAILER MODULE) AND THE GWM (GATEWAY MODULE A) FOR AN OPEN

    • Disconnect: GWM C2431.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C425B-3
      GFD385385Courtesy of FORD MOTOR COMPANY
      		 C2431-23
      C425B-2
      GFD385385Courtesy of FORD MOTOR COMPANY
      		 C2431-22

    Are the resistances less than 3 ohms? 

    Yes  CONNECT the GWM. GO to  AB4
    No  REPAIR the circuit in question.

  5. AB4 CHECK FOR CORRECT TRM (TRAILER MODULE) OPERATION

    • Ignition OFF.

    • Disconnect and inspect all the TRM 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 TRM 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 service articles: TSB, GSB, SSM or FSA. 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 TRM. REFER to: Trailer Module (TRM) .
    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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