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

WARNING: This page is about a different car, the 2013 Ford F-550 Super Duty, 2013 Ford F-450 Super Duty, 2013 Ford F-350 Super Duty, and 2013 Ford F-250 Super Duty. 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.

NOTE: Make sure the trailer brakes are electric-magnet actuated drum type brakes before proceeding with this pinpoint test.

C1 CHECK THE MESSAGE IN THE MESSAGE CENTER
- Verify that a trailer is not connected to the trailer tow connector.
- Ignition ON.
- Allow the TBC module time to wake up and prove out.
- Observe the message center.
- Does the message center display WIRING FAULT ON TRAILER?
- Yes : GO to C2.
- No : SEND the trailer to an authorized camper/trailer repair facility.
C2 CHECK THE TRAILER TOW CONNECTOR
- Ignition OFF.
- Disconnect: Trailer Tow C4099.
- Check C4099 and the 7-pin trailer tow connector for:
  - water intrusion
  - corrosion
  - pushed-out pins
  - spread terminals
- Are the connectors OK?
- Yes : GO to C3.
- No : REPAIR the affected connector(s). CLEAR any DTCs present. TEST the system for normal operation.
C3 CHECK THE TBC MODULE FOR DTCs
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: TBC Module Self-Test.
- Clear the DTCs.
- Ignition OFF.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: TBC Module Self-Test.
- Apply vehicle brakes, release vehicle brakes, carry out the TBC module self-test.
- Does DTC C2806 return?
- Yes : GO to C5.
- No : If DTC C2807 returns, GO to C4. For all other DTCs, GO to the Trailer Brake Control (TBC) Module DTC Chart .
C4 CHECK THE TBC MODULE PWM OUTPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: TBC Module C2142.
- Measure the resistance between C4099-3, circuit CAT19 (BU), harness side and ground.
  
  Fig 1: Measuring Resistance Between C4099-3, Circuit CAT19 (BU) And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10, 000 ohms?
- Yes : GO to C6.
- No : REPAIR circuit CAT19 (BU) for a short to ground. TEST the system for normal operation.
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 C4099-3, circuit CAT19, (BU), harness side and ground while operating the following lamps in turn:
  - Parking lamps
  - Stop lamps
  - Reversing lamps
    
    Fig 2: Measuring Voltage Between C4099-3, Circuit CAT19 (BU) And Ground
    Courtesy of FORD MOTOR CO.
- Is any voltage present?
- Yes : REPAIR circuit CAT19 (BU) for a short to power. 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 that 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.