Pinpoint Test E: The TBC Module Led Display Does Not Illuminate And The Trailer Brakes Are Inoperative

WARNING: This page is about a different car, the 2005 Ford Pickup, 2005 Ford F550 Super Duty, 2005 Ford F450 Super Duty, and 2005 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 .

E1 CHECK FOR ANY ANTI-LOCK BRAKE SYSTEM (ABS) MODULE DIAGNOSTIC TROUBLE CODES (DTCs)
- Key in OFF position.
- Carry out the ABS module self-test. Retrieve and record any ABS module DTCs.
- Are any ABS module DTCs retrieved?
- Yes : REFER to ANTI-LOCK CONTROL to continue diagnosis of the ABS.
- No : GO to E2.
E2 CHECK THE VOLTAGE TO THE TBC MODULE
- Disconnect: TBC Module C2142a.
- Disconnect: TBC Module C2142b.
- Key in ON position.
- Measure the voltage between the TBC module, harness side and ground as follows:
  - TBC module C2142a-1, circuit 50 (RD), harness side.
  - TBC module C2142b-3, circuit 298 (VT/OG), harness side.
    
    Fig 1: Measuring Voltage Between TBC Module, Harness Side And Ground
    Courtesy of FORD MOTOR CO.
- Are the voltages greater than 10 volts?
- Yes : GO to E3.
- No : VERIFY CJB fuse 101 (30A) is OK. If OK, REPAIR circuit 50 (RD) for an open.
  VERIFY CJB fuse 28 (10A) is OK. If OK, REPAIR circuit 298 (VT/OG) for an open.
  
  CLEAR the DTCs. REPEAT the self-test.
E3 CHECK CIRCUIT 206 (WH) FOR AN OPEN
- Key in OFF position.
- Measure the resistance between TBC module C2142-4, circuit 206 (WH), harness side and ground.
  
  Fig 2: Measuring Resistance Between TBC Module C2142-4, Circuit 206 (WH), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : GO to E4.
- No : REPAIR circuit 206 (WH) for an open. CLEAR the DTCs. REPEAT the self-test.
E4 CHECK CIRCUIT 43 (DB) FOR AN OPEN
- Disconnect: Trailer Tow C4099.
- Measure the resistance between trailer tow C4099-3, circuit 43 (DB), harness side and TBC C2142a-3, circuit 43 (DB), harness side.
  
  Fig 3: Measuring Resistance Between Trailer Tow C4099-3, Circuit 43 (DB), Harness Side And TBC C2142A-3, Circuit 43 (DB), Harness Side
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : GO to E5.
- No : REPAIR circuit 43 (DB) for an open. CLEAR the DTCs. REPEAT the self-test.
E5 CHECK CIRCUIT 43 (DB) FOR VOLTAGE
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 the voltage between trailer tow C4099-3, circuit 43 (DB), harness side and ground.
  
  Fig 4: Measuring Voltage Between C4099-3, Circuit 43 (DB) And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 1--2 volts on vehicles built before March 23rd, 2005 and greater than 10--12 volts on vehicles built March 23rd, 2005 and later?
- Yes : The TBC module is operating correctly. SEND the trailer to an authorized camper/trailer repair center for an overload condition.
- No : GO to E6.
E6 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 . 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.