Pinpoint Test C: The Trailer Brakes Are Always Engaged

WARNING: This page is about a different car, the 2012 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.

C1 CHECK FOR ANY PCM DTCs
- Ignition ON.
- Allow at least 10 seconds for all modules to wake up and prove out.
- Enter the following diagnostic mode on the scan tool: Self Test - PCM Key ON Engine OFF (KOEO).
- Retrieve and record any PCM DTCs.
- Are any PCM DTCs retrieved?
  - Yes : REFER to ELECTRONIC ENGINE CONTROLS .
  - No : GO to C2.
C2 CHECK FOR ANY TBC MODULE DTCs
- Enter the following diagnostic mode on the scan tool: Self Test - TBC Module.
- Retrieve and record any TBC module DTCs.
- Are any TBC module DTCs retrieved?
  - Yes : REFER to DTC CHARTS .
  - No : GO to C3.
C3 OBSERVE THE VEHICLE STOPLAMP OPERATION
- Monitor the vehicle stoplamps while pressing and releasing the brake pedal.
- Do the vehicle stoplamps operate correctly?
  - Yes : GO to C4.
  - No : REFER to EXTERIOR LIGHTING to diagnose the stoplamp switch.
C4 CHECK THE TBC MODULE OUTPUT
NOTE: Every 4 seconds a voltage pulse is applied as a trailer connectivity test.
- Ignition ON.
- Make sure the brake pedal is not pressed and the manual slider switch is not being applied.
- Measure the voltage between 7-pin trailer tow connector electric brake supply pin, component side and ground.
  
  Fig 1: Measuring Voltage Between 7-Pin Trailer Tow Connector Electric Brake Supply Pin, Component Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage approximately 0.3-0.4 volt?
  - Yes : The TBC module and vehicle wiring are operating correctly. SEND the trailer to an authorized camper/trailer repair center.
  - No : GO to C5.
C5 CHECK THE TBC MODULE PWM OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: TBC Module C2142.
- Ignition ON.
- Measure the voltage between 7-pin trailer tow connector electric brake supply pin, component side and ground.
  
  Fig 2: Measuring Voltage Between 7-Pin Trailer Tow Connector Electric Brake Supply Pin, Component Side And Ground
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
  - Yes : REPAIR the circuit. TEST the system for normal operation.
  - No : GO to C6.
C6 CHECK FOR CORRECT TBC MODULE OPERATION
- Disconnect the TBC module connector.
- Check for:
  - corrosion
  - damaged pins
  - pushed-out pins
- Connect the TBC module connector and make sure it seats correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
  - Yes : INSTALL a new TBC module. REFER to TRAILER BRAKE CONTROL (TBC) MODULE . TEST the system for normal operation.
  - No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. TEST the system for normal operation.