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

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.

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

A1 CHECK THE MESSAGE IN THE MESSAGE CENTER
- Verify that a trailer is not connected to the trailer tow connector.
- Ignition ON.
- Allow at least 10 seconds for all modules to wake up and prove out.
- Observe the message center.
- Does the message center display WIRING FAULT ON TRAILER?
  - Yes : GO to A2.
  - No : SEND the trailer to an authorized camper/trailer repair center.
A2 CHECK THE TBC MODULE FOR DTCs
- Using a scan tool, clear the TBC module DTCs.
- Ignition OFF.
- Wait at least 5 seconds to allow the TBC module to sleep (power down).
- 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 - TBC Module.
- Are any DTCs present?
  - Yes : For DTC C2806 or C2807, GO to A3.
    For all other DTCs, REFER to the Trailer Brake Control (TBC) Module DTC Chart .
  - No : The TBC module and vehicle wiring are operating correctly. SEND the trailer to an authorized camper/trailer repair center. CLEAR the DTCs. REPEAT the self-test.
A3 CHECK THE TBC MODULE FOR DTCs WITH THE TRAILER TOW CONNECTOR DISCONNECTED
- Disconnect: Trailer Tow Connector C439A.
- Using the scan tool, clear the TBC module DTCs.
- Enter the following diagnostic mode on the scan tool: Self Test - TBC Module.
- Does DTC C2806 or C2807 return?
  - Yes : For DTC C2806, GO to A5.
    For DTC C2807, GO to A4.
  - No : INSTALL a new trailer tow connector. CLEAR the DTCs. REPEAT the self-test.
A4 CHECK THE TBC MODULE PWM OUTPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: TBC module C2142.
- Measure the resistance between the trailer tow connector C439A-3, circuit CAT19 (BU), harness side and ground.
  
  Fig 1: Measuring Resistance Between Trailer Tow Connector C439A-3, Circuit CAT19 (BU), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10, 000 ohms?
  - Yes : GO to A6.
  - No : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
A5 CHECK THE TBC MODULE PWM OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition ON.
- Measure the voltage between the trailer tow connector C439A-3, circuit CAT19 (BU), harness side and ground.
  
  Fig 2: Measuring Voltage Between Trailer Tow Connector C439A-3, Circuit CAT19 (BU), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
  - Yes : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  - No : GO to A6.
A6 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.