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Pinpoint Test C: The Message Center Displays Wiring Fault On Trailer

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
  1. Refer to TRAILER/CAMPER ADAPTER for schematic and connector information.

    Normal Operation and Fault Conditions 

    The braking energy provided to the trailer is modulated with a PWM signal which varies between 0 volt and battery voltage, according to the TRM gain setting, the higher the duty cycle the more braking power available. The TRM varies the PWM signal based on various inputs such as vehicle speed, the brake torque message, BPP switch input, the manual slider switch and the gain buttons. With the vehicle stationary and with the manual slider switch fully to the left with a gain of 10, there should be more than 11 volts supplied to the trailer tow connector. Without a trailer connected, the TRM sends a voltage pulse to the trailer tow connector every 4 seconds as a trailer connectivity test.

    REFER to: Auxiliary Brake System - System Operation and Component Description .

    DTC Fault Trigger Conditions 

    DTC Description Fault Trigger Condition
    TBM U3000:1D Control Module: Circuit Current Out Of Range This DTC sets in continuous memory and on-demand if Trailer Brake Output current is flowing in the OFF state.
    TBM U3000:1C Control Module: Circuit Voltage Out Of Range This DTC sets in continuous memory and on-demand if Trailer Brake Output current is flowing and the HS FET gate voltage is out of range.
    TBM U3000:12 Control Module: Circuit Short To Battery This DTC sets in continuous memory and on-demand if Trailer Brake Output current is flowing and the HS FET is stuck ON.
    TBM B148A:11 Trailer Brake Output: Circuit Short To Ground This DTC sets in continuous memory when the ignition is set to RUN or during the on-demand self test if the current draw on the PWM output circuit is greater than 49 amps.
    TBM B148A:12 Trailer Brake Output: Circuit Short To Battery This DTC sets in continuous memory when the ignition is set to RUN and vehicle speed is greater than 3 km/h (2 mph) or during the on-demand self test if the PWM output is greater than 7.1 volts when not  braking or greater than 4 volts during  braking.

    Possible Sources 

    • Wiring, terminals or connectors
    • TRM
    • Trailer
    • Trailer Tow Switch

  2. NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.

  3. C1 VERIFY TBM (TRAILER BRAKE CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)

    NOTE: The TRM is a combined TBM and Trailer Lighting Module.

    • Verify a trailer is not  connected to the trailer tow connector.

    • Ignition ON.

    • Using a diagnostic scan tool, carry out the TBM self-test.

    • Clear the Diagnostic Trouble Codes (DTCs).

    • Test drive the vehicle in the following manner:

      • maintain a speed greater than 5 km/h (3 mph)
      • turn the headlights ON
      • lightly apply the brakes for more than 5 seconds
      • activate the left and right turn signals

    • Ignition OFF.

    • Ignition ON.

    • Wait at least 10 seconds for all modules to wake up and prove out.

    • NOTE: Diagnostic Trouble Codes (DTCs) U3000:12, U3000:1C or U3000:1D set with either B148A:11 or B148A:12

      Using a diagnostic scan tool, carry out the TBM self-test.

    Is DTC B148A:11 or B148A:12 present? 

    Yes  GO to  C2
    No  For all other TRM Diagnostic Trouble Codes (DTCs), GO to the DTC Chart: TBM in Diagnostic Trouble Code (DTC) Chart . If no Diagnostic Trouble Codes (DTCs) return, the system is operating correctly at this time. INSPECT the 7-pin trailer tow connector C4099 for water intrusion, corrosion, pushed-out pins and spread terminals. REPAIR or INSTALL new as necessary.

  4. C2 CHECK THE TRAILER TOW CONNECTOR

    • Ignition OFF.

    • Disconnect in-line connector C4099.

    • Using a diagnostic scan tool, carry out the TBM self-test.

    • Clear the Diagnostic Trouble Codes (DTCs).

    • Test drive the vehicle in the following manner:

      • maintain a speed greater than 5 km/h (3 mph)
      • turn the headlights ON
      • lightly apply the brakes for more than 5 seconds
      • activate the left and right turn signals

    • Ignition OFF.

    • Ignition ON.

    • Wait at least 10 seconds for all modules to wake up and prove out.

    • Using a diagnostic scan tool, carry out the TBM self-test.

    Is DTC B148A:11 or B148A:12 present? 

    Yes  For DTC B148A:11, GO to  C3 For DTC B148A:12, GO to  C4
    No  INSTALL a new 7-pin trailer tow connector.

  5. C3 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) PWM (PULSE WIDTH MODULATION) OUTPUT CIRCUIT FOR A SHORT TO GROUND

    • Ignition OFF.

    • Connect in-line connector C4099.

    • Disconnect TRM C2498C.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C4099-3
      GFD552276Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance greater than 10, 000 ohms? 

    Yes  GO to  C4
    No  REPAIR the circuit.

  6. C4 CHECK THE TRM (TRAILER MODULE) PWM (PULSE WIDTH MODULATION) OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE

    • Ignition OFF.

    • Connect in-line connector C4099.

    • Disconnect TRM C2498C.

    • Ignition ON.

    • Operate the park lamps and measure:
      Positive Lead Measurement / Action Negative Lead
      C4099-3
      GFD552275Courtesy of FORD MOTOR COMPANY
      		 Ground

    • Operate the stoplamps and measure:
      Positive Lead Measurement / Action Negative Lead
      C4099-3
      GFD552275Courtesy of FORD MOTOR COMPANY
      		 Ground

    • Operate the reversing lamps and measure:
      Positive Lead Measurement / Action Negative Lead
      C4099-3
      GFD552275Courtesy of FORD MOTOR COMPANY
      		 Ground

    At anytime, was any voltage present? 

    Yes  REPAIR the circuit. REFER to the OEM WIRING DIAGRAMS to identify the possible causes of the circuit short.
    No  GO to  C5

  7. C5 CHECK FOR CORRECT TRM (TRAILER MODULE) OPERATION

    • Disconnect TRM C2498C (if not previously disconnected).

    • Using a good light source, inspect the connector 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

    • Connect TRM C2498C and make sure it seats and latches correctly.

    • Test drive the vehicle in the following manner:

      • maintain a speed greater than 5 km/h (3 mph)
      • turn the headlights ON
      • lightly apply the brakes for more than 5 seconds
      • activate the left and right turn signals

    • Ignition OFF.

    • Ignition ON.

    • Wait at least 10 seconds for all modules to wake up and prove out.

    • Using a diagnostic scan tool, carry out the TBM self-test.

    Is DTC B148A:11 or B148A:12 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 module. REFER to: Trailer Module (TRM) .
    No  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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