Pinpoint Test D: When The Ignition Key Is Turned To The Run Position, The TBC Module Display Does Light Up/Prove Out But The Trailer Brakes Are Inoperative

WARNING: This page is about a different car, the 2009 Ford RV Cutaway, 2009 Ford Econoline, 2009 Ford E450 Super Duty, and 2009 Ford Cutaway. 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.

D1 CHECK FOR ANY ABS MODULE DTCs
- Connect the scan tool.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self Test - ABS Module.
- Retrieve and record any ABS module DTCs.
- Are any ABS module DTCs retrieved?
- Yes: REFER to VEHICLE DYNAMIC SYSTEMS .
- No: Go to D2 .
D2 CHECK THE TBC BRAKE ON/OFF (BOO_TBC) PID
- Enter the following diagnostic mode on the scan tool: DataLogger - TBC Module.
- Monitor the BOO_TBC PID while pressing and releasing the brake pedal.
- Does the PID agree with the brake pedal position?
- Yes: Go to D4.
- No: Go to D3 .
D3 CHECK THE PCM BOO PID
- Enter the following diagnostic mode on the scan tool: DataLogger - PCM.
- Monitor the BOO PID while pressing and releasing the brake pedal.
- Does the PID agree with the brake pedal position?
- Yes: REFER to MODULE COMMUNICATIONS NETWORK to diagnose the HS-CAN bus.
- No: REFER to EXTERIOR LIGHTING to diagnose the stoplamp (BPP ) switch.
D4 CHECK THE VOLTAGE TO THE TBC MODULE
- Ignition OFF.
- Disconnect: TBC Module C2142.
- Ignition ON.
- Measure the voltage between ground and:
  - TBC module C2142-8, circuit SBB18 (YE/RD), harness side.
  - TBC module C2142-12, circuit CBP33 (WH/BN), harness side.
  Fig 1: Measuring Voltage Between Ground And TBC Module C2142-8, Circuit SBB18 (YE/RD), Harness Side
- Are the voltages greater than 10 volts?
- Yes: Go to D5 .
- No: VERIFY BJB fuse 18 (30A) is OK. If OK, REPAIR circuit SBB18 (YE/RD).
  VERIFY SJB fuse 33 (10A) is OK. If OK, REPAIR circuit CBP33 (WH/BN).
  
  If either fuse is not OK, refer to appropriate WIRING DIAGRAMS article to identify the possible causes of the circuit short.
  
  CLEAR the DTCs. REPEAT the self-test.
D5 CHECK THE TBC MODULE GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between TBC module C2142-11, circuit GD116 (BK/VT), harness side and ground.
  
  Fig 2: Measuring Resistance Between TBC Module C2142-11, Circuit GD116 (BK/VT), Harness Side And Ground
- Is the resistance less than 5 ohms?
- Yes: Go to D6 .
- No: REPAIR circuit GD116 (BK/VT). CLEAR the DTCs. REPEAT the self-test.
D6 CHECK THE TBC MODULE PWM OUTPUT CIRCUIT FOR AN OPEN
- Measure the resistance between trailer tow 7-pin trailer tow connector pin-3, circuit CAT19 (BU), harness side and TBC module C2142-14, circuit CAT19 (BU), harness side.
  
  Fig 3: Measuring Resistance Between Trailer Tow 7-Pin Trailer Tow Connector Pin-3, Circuit CAT19 (BU) And TBC Module C2142-14, Circuit CAT19 (BU)
- Is the resistance less than 5 ohms?
- Yes: Go to D7 .
- No: REPAIR circuit CAT19 (BU). CLEAR the DTCs. REPEAT the self-test.
D7 CHECK THE TBC MODULE FOR MAXIMUM OUTPUT
NOTE: Battery voltage must be greater than 10 volts.
- Ignition OFF.
- Connect: TBC Module C2142.
- Ignition ON.
- Input a gain setting of 10 into the TBC module.
- NOTE: If the manual slider switch is held to the full left position for more than 5 minutes, the TBC module will automatically shut down.
- 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 7-pin trailer tow connector pin-3, circuit CAT19 (BU), harness side and ground.
  
  Fig 4: Measuring Voltage Between Trailer Tow 7-Pin Trailer Tow Connector Pin-3, Circuit CAT19 (BU), Harness Side And Ground
- 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 D8 .
D8 CHECK FOR CORRECT TBC MODULE OPERATION
- Disconnect: TBC Module C2142.
- Check the connector for:
  - corrosion.
  - pushed-out pins.
  - spread terminals.
- Connect: TBC Module C2142.
- Make sure the connector is seated correctly, then 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.