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Tim
Tim, Ford Technician
Category: Ford
Satisfied Customers: 3580
Experience:  Ford Senior Master tech, ASE certified
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2006 F-350: The trailer fault indicator..terminal..light goes

Resolved Question:

2006 F-350   The trailer fault indicator has started coming on. The truck has a western plow on it. When I put the test light on the trailer plug on the electric brake terminal, the fault light goes out. This problem occurs only when it snows or at the car wash. It says trailer fault when not hooked to a trailer. When a trailer is behind, this problem doesn't exist. Do you have any ideas??     Mike
Submitted: 5 years ago.
Category: Ford
Expert:  Tim replied 5 years ago.
It sounds like you are getting water intrusion in the trailer connector. Clean the connector out really good and pack the connector with dielectrical grease this should take care of the concern.
Customer: replied 5 years ago.
I pulled the connector apart and greased terminals and it still gives the code when I apply the brake or turn on the left signal. Is there another connection to check ?
Expert:  Tim replied 5 years ago.

If there is no water intrusion than you either have a wiring problem or module problem.

Do you have a volt/ohm meter?

Customer: replied 5 years ago.
Everything looked fine, I didn't see any moisture. Yes I do have a meter.
Expert:  Tim replied 5 years ago.

Here is the pinpoint test for the trailer fault. It is easier if you have the trailer brake module scanned for codes.

 

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

Test StepResult / Action to Take
D1 CHECK THE TRAILER TOW CONNECTOR
  • Ignition OFF.
  • Disconnect: C4099 From the 7-Pin Trailer Tow Connector.
  • Check C4099 and the 7-pin trailer tow connector for:
    • water intrusion.
    • corrosion.
    • pushed-out pins.
  • Is trailer tow C4099 OK?
Yes
GO to D2.

No
REPAIR trailer tow C4099.
D2 CHECK THE TBC MODULE DTCs
  • Connect the scan tool.
  • Ignition ON.
  • Using the scan tool, clear the DTCs and cycle the ignition switch.
  • Enter the following diagnostic mode on the scan tool: Self-Test - TBC.
  • 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) Chart and continue diagnostics.

If no DTCs returned, the system is operating correctly at this time. INSPECT the 7-pin trailer tow connector for evidence of water intrusion or corrosion. INSPECT the trailer tow C4099 harness for evidence of chaffed wiring or improper wire repair. REPAIR wiring as necessary. CLEAR the DTCs. REPEAT the self-test.
D3 CHECK CIRCUIT 43 (DB) FOR A SHORT TO GROUND
  • Ignition OFF.
  • Disconnect: TBC Module C2142A.
  • Disconnect: TBC Module C2142B.
  • Measure the resistance between C4099-3, circuit 43 (DB), harness side and ground.
  • 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 THE TBC MODULE OUTPUT 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 the 7-pin trailer tow connectors.

  • Ignition ON.
  • NOTE: Make sure the brake pedal is not pressed and the manual slider switch is not being applied.
  • Measure the voltage between C4099-3, circuit 43 (DB), harness side and ground while operating the following lamps in turn:
    • Parking lamps
    • Left turn signal
    • Right turn signal
    • Reversing lamps

  • Is steady voltage of more than 0.5 volt present?
Yes
REPAIR circuit 43 (DB). CLEAR the DTCs. REPEAT the self-test.

No
The system is operating correctly at this time. INSPECT the 7-pin trailer tow connector for evidence of water intrusion or corrosion. INSPECT the trailer tow C4099 harness for evidence of chaffed wiring or improper wire repair. REPAIR wiring as necessary. CLEAR the DTCs. REPEAT the self-test.
D5 CHECK THE TBC MODULE FOR MAXIMUM OUTPUT

    NOTE: Battery voltage must be greater than 10 volts.

  • Ignition OFF.
  • Connect: TBC Module C2142A.
  • Connect: TBC Module C2142B.
  • Ignition ON.
  • Have an assistant press the manual slider switch fully to the left with a gain of 10 on the TBC module.
  • Measure voltage between C4099-3, circuit 43 (DB), harness side and ground.
  • Is the voltage greater than 10-12 volts?
Yes
The system is operating correctly at this time. INSPECT the 7-pin trailer tow connector for evidence of water intrusion or corrosion. INSPECT the trailer tow C4099 harness for evidence of chaffed wiring or improper wire repair. REPAIR wiring as necessary. CLEAR the DTCs. REPEAT the self-test.

No
GO to D6.
D6 CHECK CIRCUIT 43 (DB) FOR AN OPEN
  • Ignition OFF.
  • Disconnect: TBC Module C2142A.
  • Measure resistance between C4099-3, circuit 43 (DB), harness side and TBC C2142A-3, circuit 43 (DB), harness side.
  • 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. INSPECT the 7-pin trailer tow connector for evidence of water intrusion or corrosion. INSPECT the trailer tow C4099 harness for evidence of chaffed wiring or improper wire repair. REPAIR wiring as necessary. CLEAR the DTCs. REPEAT the self-test.
Tim, Ford Technician
Category: Ford
Satisfied Customers: 3580
Experience: Ford Senior Master tech, ASE certified
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