Pinpoint Test B: The Trailer Brakes Are Always Engaged
WARNING: This page is about a different car, the 2013 Ford F-550 Super Duty, 2013 Ford F-450 Super Duty, 2013 Ford F-350 Super Duty, and 2013 Ford F-250 Super Duty. 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.
- B1 CHECK FOR ANY TBC MODULE OR PCM DTCs
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: TBC Module Self-Test.
- Enter the following diagnostic mode on the scan tool: PCM Self-Test.
- Retrieve and record any TBC module or PCM DTCs.
- Are any TBC module or PCM DTCs retrieved?
- Yes
: For TBC module DTCs, REFER to DTC CHART .
For PCM DTCs, REFER to ELECTRONIC ENGINE CONTROLS - GASOLINE ENGINES (gas engine) or ELECTRONIC ENGINE CONTROLS - DIESEL ENGINES (diesel engine).
- No : GO to B2.
- B2 OBSERVE THE VEHICLE STOPLAMP OPERATION
- Monitor the vehicle stoplamps while pressing and releasing the brake pedal.
- Do the vehicle stoplamps operate correctly?
- Yes : GO to B3.
- No : REFER to EXTERIOR LIGHTING to diagnose the stoplamp switch.
- B3 CHECK THE TBC MODULE OUTPUT NOTE: Every 4 seconds a voltage pulse is applied as a trailer connectivity test.
- Ignition OFF.
- Disconnect: Trailer Tow C4099.
- Ignition ON.
- 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 CAT19 (BU), harness side and ground.
- Is steady voltage indicated?
- Yes : GO to B4.
- No : The TBC module and vehicle wiring are operating correctly. SEND the trailer to an authorized camper/trailer repair facility.
- B4 CHECK THE TBC MODULE PWM OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: TBC Module C2142.
- Ignition ON.
- Measure the voltage between trailer tow C4099-3, circuit CAT19 (BU), harness side and ground.
- Is any voltage present?
- Yes : REPAIR circuit CAT19 (BU) for a short to voltage. TEST the system for normal operation.
- No : GO to B5.
- B5 CHECK FOR CORRECT TBC MODULE OPERATION
- Disconnect the TBC module connector.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the TBC module connector and make sure that it seats 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.