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

WARNING: This page is about a different car, the 2014 Ford F-150. 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 VERIFY TBC MODULE DTCs
- Verify a trailer is not connected to the trailer tow connector.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: TBC Module Self-Test.
- Clear the 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.
- Enter the following diagnostic mode on the scan tool: TBC Module Self-Test.
Is DTC C2806 or C2807 present?
- Yes : GO to A2 .
- No : For all other TBC module DTCs, GO to the TBC MODULE DTC CHART .
  If no DTCs return, the system is operating correctly at this time. INSPECT the 7-pin trailer tow connector for water intrusion, corrosion, pushed-out pins and spread terminals. REPAIR or INSTALL new as necessary.
  
  If the 7-pin trailer tow connector is OK, SEND the trailer to an authorized camper/trailer repair facility.
A2 CHECK THE TRAILER TOW CONNECTOR
- Ignition OFF.
- Disconnect: Trailer Tow C439A .
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: TBC Module Self-Test.
- Clear the 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.
- Enter the following diagnostic mode on the scan tool: TBC Module Self-Test.
Is DTC C2806 or C2807 present?
- Yes : For DTC C2806, GO to A4.
  For DTC C2807, GO to A3 .
- No : INSTALL a new 7-pin trailer tow connector. CLEAR any DTCs present. TEST the system for normal operation.
A3 CHECK THE TBC MODULE PWM OUTPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Connect: Trailer Tow C439A .
- Disconnect: TBC Module C2142 .
- Measure the resistance between C439A-3 , circuit CAT19 (BU), harness side and ground.
  
  Fig 1: Measuring Resistance Between 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 A5.
- No : REPAIR circuit CAT19 (BU) for a short to ground. TEST the system for normal operation.
A4 CHECK THE TBC MODULE PWM OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Connect: Trailer Tow C439A .
- Disconnect: TBC Module C2142 .
- Ignition ON.
- Measure the voltage between C439A-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 C439A-3, Circuit CAT19, (BU), Harness Side 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 A5 .
A5 CHECK FOR CORRECT TBC MODULE OPERATION
- Ignition OFF.
- Inspect the TBC module connector.
- Repair:
  - corrosion (install a new connector or terminal - clean 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 the TBC module connector and make sure that it seats 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.
- Enter the following diagnostic mode on the scan tool: TBC Module Self-Test.
Is DTC C2806 or C2807 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.