PINPOINT TEST D: DTCs C2806, C2807 AND C2808 - TRAILER BRAKES CIRCUIT FAILURE

WARNING: This page is about a different car, the 2006 Ford Pickup, 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Use the flex probe kit for all test connections to prevent damage to the wiring terminals. Do not use standard multimeter probes.

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

D1 CHECK THE TRAILER TOW CONNECTOR
- Key in OFF position.
- Disconnect: Trailer Tow C4099.
- Check trailer tow C4099 for:
  - corrosion.
  - pushed-out pins.
- Is trailer tow C4099 OK?
Yes : GO to D2.

No : REPAIR trailer tow C4099.
D2 CHECK THE DTCs
- Connect the scan tool.
- Key in ON position.
- Clear the DTCs and cycle the ignition switch.
- Retrieve the DTCs.
- Did DTC C2806, C2807 or C2808 return?
Yes : For DTC C2806, GO to D4.

For DTC C2807, GO to D3.

For DTC C2808, GO to D3.

No : If other DTCs are retrieved, GO to TRAILER BRAKE CONTROL (TBC) MODULE DIAGNOSTIC TROUBLE CODE (DTC) INDEX and continue diagnostics.

If no DTCs returned, the customer trailer may be at fault. SEND the trailer to an authorized camper/trailer repair center.
D3 CHECK CIRCUIT 43 (DB) FOR A SHORT TO GROUND
- Key in OFF position.
- Disconnect: TBC Module C2142a.
- Disconnect: TBC Module C2142b.
- Measure the resistance between trailer tow C4099-3, circuit 43 (DB), harness side and ground.
  
  Fig 1: Checking Circuit 43 (DB) For Short To Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
Yes : GO to D5.

No : REPAIR circuit 43 (DB). CLEAR the DTCs. REPEAT the self-test.
D4 CHECK CIRCUIT 43 (DB) FOR A SHORT TO VOLTAGE
NOTE: Every 4 seconds a voltage pulse is applied to circuit 43 (DB) to determine whether or not a trailer is connected to trailer tow C4099.
- Key in ON position.
- Make sure the brake pedal is not pressed and the manual slider switch is not being applied.
- Measure the voltage between trailer tow C4099-3, circuit 43 (DB), harness side and ground.
  
  Fig 2: Measuring Voltage Between connector And Ground
  Courtesy of FORD MOTOR CO.
- Is a steady voltage of more than 0.5 volt present?
Yes : REPAIR circuit 43 (DB). CLEAR the DTCs. REPEAT the self-test.

No : The TBC module and vehicle wiring are operating correctly. SEND the trailer to an authorized camper/trailer repair center.
D5 CHECK CIRCUIT 43 (DB) VOLTAGE OUTPUT
NOTE: Battery voltage must be greater than 10 volts.
- Key in OFF position.
- Connect: TBC Module C2142a.
- Connect: TBC Module C2142b.
- Key in ON position.
- Have an assistant press the manual slider switch fully to the left with a gain of 10 on the TBC module.
- Measure voltage between trailer tow C4099-3, circuit 43 (DB), harness side and ground.
  
  Fig 3: Measuring Voltage Between connector And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10-12 volts?
Yes : The TBC module is operating correctly. SEND the trailer to an authorized camper/trailer repair center for an overload condition.

No : GO to D6.
D6 CHECK CIRCUIT 43 (DB) FOR AN OPEN
- Key in OFF position.
- Disconnect: TBC Module C2142a.
- Measure resistance between trailer tow C4099-3, circuit 43 (DB), harness side and TBC C2142a-3, circuit 43 (DB), harness side.
  
  Fig 4: Checking Circuit 43 (DB) For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : GO to D7.

No :REPAIR circuit 43 (DB). CLEAR the DTCs. REPEAT the self-test.
D7 CHECK FOR CORRECT TBC MODULE OPERATION
- Disconnect all the TBC module connectors.
- Check for:
  - corrosion.
  - pushed-out pins.
  - spread terminals.
- Connect all the TBC module connectors and make sure that they are seated 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 in this section. CLEAR the DTCs. REPEAT the self-test.

No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.