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Home >> Ford >> 2021 >> Expedition Platinum, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 236 (Auxiliary Brake System) >> Diagnosis And Testing >> Auxiliary Brake System - Vehicles With: Trailer Brake Control >> Pinpoint Tests >> Pinpoint Test A : The Trailer Brakes Are Inoperative >> Pinpoint Test A : The Trailer Brakes Are Inoperative

Pinpoint Test A : The Trailer Brakes Are Inoperative

WARNING: This page is about a different car, the 2019 Ford F-550 Super Duty, 2019 Ford F-450 Super Duty, 2019 Ford F-350 Super Duty, and 2019 Ford F-250 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.

  1. A1 CHECK FOR BCM (BODY CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)

    • Ignition ON.

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

    Are any Diagnostic Trouble Codes (DTCs) present in the BCM? 

    Yes  DIAGNOSE all BCM Diagnostic Trouble Codes (DTCs). REFER to: Body Control Module (BCM) .
    No  GO to  A2

  2. A2 CHECK FOR ABS (ANTI-LOCK BRAKE SYSTEM) MODULE DIAGNOSTIC TROUBLE CODES (DTCS)

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

    Are any Diagnostic Trouble Codes (DTCs) present in the ABS module? 

    Yes  DIAGNOSE all ABS module Diagnostic Trouble Codes (DTCs). REFER to: ANTI-LOCK BRAKE SYSTEM (ABS) AND STABILITY CONTROL
    No  GO to  A3

  3. A3 CHECK FOR TBM (TRAILER BRAKE CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)

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

    Does the TBM communicate with the diagnostic scan tool? 

    Yes  If there are Diagnostic Trouble Codes (DTCs) in the TBM, DIAGNOSE all TBM Diagnostic Trouble Codes (DTCs). GO to the DTC Chart: Trailer Brake Control Module (TBM)  If there are no Diagnostic Trouble Codes (DTCs) in the TBM, GO to  A4
    No  DIAGNOSE the TBM does not communicate with the diagnostic scan tool. REFER to: Communications Network .

  4. A4 CHECK THE BCM (BODY CONTROL MODULE) BRAKE SWITCH 2 (BOO_2) PID (PARAMETER IDENTIFICATION)

    • Using a diagnostic scan tool, monitor the BCM BOO_2 PID while pressing and releasing the brake pedal.

    Does the BOO_2 PID display ON with the brake pedal pressed and OFF with the brake pedal released? 

    Yes  GO to  A5
    No  DIAGNOSE the vehicle stoplamps. REFER to: Stoplamps .

  5. A5 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) BRAKE SWITCH (BRAKE_SW) PID (PARAMETER IDENTIFICATION)

    • Using a diagnostic scan tool, monitor the TBM BRAKE_SW PID while pressing and releasing the brake pedal.

    Does the BRAKE_SW PID display ON with the brake pedal pressed and OFF with the brake pedal released? 

    Yes  GO to  A6
    No  DIAGNOSE the BPP (stoplamp) switch. REFER to: Stoplamps .

  6. A6 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) OUTPUT

    NOTE: Battery voltage must be greater than 10 volts.

    • Ignition ON.

    • NOTE: If the manual slider switch is held to the full left position for more than 5 minutes, the TBM automatically shuts down.
      NOTE: Do not apply the brake pedal during this test. Brake pedal apply is speed sensitive, sitting still the max TBM output during an brake pedal apply is 15 percent.

      Have an assistant press the manual slider switch fully to the left with a gain of 10 on the TBM.

    • NOTE: Testing is performed at the 7 way trailer tow connector.

      Measure:

      5th Wheel Inside Truck Bed 

      Positive Lead Measurement / Action Negative Lead
      Refer to C439-3
      GFD405393Courtesy of FORD MOTOR COMPANY
      		 Ground

      Rear Bumper 

      Positive Lead Measurement / Action Negative Lead
      Refer to C4099-3
      GFD405393Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage 10 volts? 

    Yes  The TBM is operating correctly.
    SEND  the trailer to an authorized camper/trailer repair center.
    No  GO to  A7

  7. A7 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) PWM (PULSE WIDTH MODULATION) OUTPUT CIRCUIT FOR A SHORT TO GROUND

    • Ignition OFF.

    • Disconnect TBM C2142.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      Refer to C2142-14
      GFD404793Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance greater than 10, 000 ohms? 

    Yes  GO to  A8
    No  REPAIR the circuit.

  8. A8 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) PWM (PULSE WIDTH MODULATION) OUTPUT CIRCUIT FOR AN OPEN

    • Measure:

      5th Wheel Inside Truck Bed 

      Positive Lead Measurement / Action Negative Lead
      Refer to C2142-14
      GFD404793Courtesy of FORD MOTOR COMPANY
      		 Refer to C439-3

      Rear Bumper 

      Positive Lead Measurement / Action Negative Lead
      Refer to C2142-14
      GFD404793Courtesy of FORD MOTOR COMPANY
      		 Refer to C4099-3

    Is the resistance less than 3 ohms? 

    Yes  GO to  A9
    No  REPAIR the circuit.

  9. A9 VERIFY ALL WIRING CONNECTIONS

    • Disconnect TBM C2142.

    • NOTE: C439 connects to the back of the 7 way trailer tow connector.

      Disconnect C439 (If equipped with 5th wheel).

    • NOTE: C4099 connects to the back of the 7 way trailer tow connector.

      Disconnect C4099

    • Disconnect all in-line electrical connectors between the TBM and the 7 way connector.

    • 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  GO to  A10
    No  REPAIR the affected connectors or terminals. Refer to GROUNDS for schematic and connector information.

  10. A10 CHECK FOR CORRECT TBM (TRAILER BRAKE CONTROL MODULE) OPERATION

    • Connect all in-line electrical connectors between the TBM and the 7 way connector. Make sure they seat and latch correctly.

    • NOTE: C439 connects to the back of the 7 way trailer tow connector.

      Connect C439 (If equipped with 5th wheel). Make sure it seats and latches correctly.

    • NOTE: C4099 connects to the back of the 7 way trailer tow connector.

      Connect C4099. Make sure it seats and latches correctly.

    • Connect TBM C2142. Make sure it seats and latches correctly.

    • Operate the system and verify 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 the TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new TBM. REFER to: Trailer Brake Control Module (TBM) .
    No  The condition causing the concern is not present at this time. The concern is intermittent and may have been caused by a loose or corroded connector, low battery voltage or an excessive load on the HS-CAN1 or HS-CAN2.
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