Pinpoint Test A : The Trailer Brakes Are Inoperative

WARNING: This page is about a different car, the 2016 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.

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

A1 CHECK FOR ANY ABS MODULE OR PCM DTCs

Ignition ON.

Using a diagnostic scan tool, carry out the ABS module self-test.

Using a diagnostic scan tool, carry out the PCM KOEO self-test.

Retrieve and record all ABS module and PCM DTCs.

Are any DTCs present in the ABS module or PCM?

Yes	For ABS DTCs, REFER to Diagnosis and Testing in Anti-Lock Brake System (ABS) and Stability Control .For PCM DTCs, REFER to Diagnosis and Testing in Electronic Engine Controls .
No	GO to A2.

A2 CHECK FOR TBC MODULE DTCs
- Using a diagnostic scan tool, carry out the TBC module self-test.
Are any TBC module DTCs present?

Yes GO to the DTC Chart: TBC Module .

No GO to A3.

A3 CHECK THE VEHICLE STOPLAMP OPERATION

Monitor the vehicle stoplamps while pressing and releasing the brake pedal.

Do the vehicle stoplamps operate correctly?

Yes	GO to A4.
No	REFER to Diagnosis and Testing in Exterior Lighting to diagnose the stoplamp switch.

A4 CHECK THE TBC MODULE BRAKE ON / OFF (BOO_TBC) PID

Using a diagnostic scan tool, monitor the BOO_TBC PID while pressing and releasing the brake pedal.

Does the PID display "Active" with the pedal pressed "Inactive" with the pedal released?

Yes	GO to A5.
No	VERIFY SJB fuse 31 (5A) is OK. If not OK, REFER to the OEM Electrical Wiring Diagram Introduction to identify the cause of the circuit short. If OK, REPAIR the TBC module brake on / off input circuit for an open. Refer to Trailer/Camper Adapter , for schematic and connector information.

A5 CHECK THE TBC MODULE OUTPUT

NOTE: Battery voltage must be greater than 10 volts.

NOTE: If the manual slider switch is held to the full left position for more than 20 minutes, the TBC module automatically shuts down.

Have an assistant press the manual slider switch fully to the left with a gain of 10 on the TBC module.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C4099-3	Courtesy of FORD MOTOR COMPANY	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.
No	GO to A6.

A6 CHECK THE TBC MODULE PWM OUTPUT CIRCUIT FOR AN OPEN

Ignition OFF.

Disconnect trailer tow C4099 .

Disconnect TBC module C2142 .

Measure:

Positive Lead	Measurement / Action	Negative Lead
C4099-3	Courtesy of FORD MOTOR COMPANY	C2142-14

Is the resistance less than 3 ohms?

Yes	GO to A7.
No	REPAIR the circuit.

A7 CHECK FOR CORRECT TBC MODULE OPERATION

Inspect TBC module C2142 .

Repair:
- corrosion (install new connector or terminal - clean module pins)
- damaged or bent pins - install new terminals or pins
- pushed-out pins - install new pins as necessary

Connect TBC module C2142 , make sure it seats and latches correctly.

Connect trailer tow C4099 , make sure it seats and latches correctly.

Operate the system and verify the concern is still present.

Is the concern still present?

Yes	CHECK OASIS for any applicable TSBs. If a TSB exists for this concern, DISCONTINUE this test and FOLLOW the TSB instructions. If no TSBs address this concern, INSTALL a new TBC module. REFER to Trailer Brake Control (TBC) Module .
No	The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.