Pinpoint Test A : The Trailer Brakes Are Inoperative

WARNING: This page is about a different car, the 2018 Ford F-550 Super Duty, 2018 Ford F-450 Super Duty, 2018 Ford F-350 Super Duty, and 2018 Ford F-250 Super Duty. 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.

A1 CHECK FOR BCM (BODY CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)
- Ignition ON.
- Using a diagnostic scan tool, carry out the BCM self-test.
Are any Diagnostic Trouble Codes (DTCs) present in the BCM?

Yes DIAGNOSE all BCM Diagnostic Trouble Codes (DTCs). REFER to: Body Control Module (BCM) .

No GO to A2

A2 CHECK FOR ABS (ANTI-LOCK BRAKE SYSTEM) MODULE DIAGNOSTIC TROUBLE CODES (DTCS)
- Using a diagnostic scan tool, carry out the ABS module self-test.
Are any Diagnostic Trouble Codes (DTCs) present in the ABS module?

Yes DIAGNOSE all ABS module Diagnostic Trouble Codes (DTCs). REFER to: Anti-Lock Brake System (ABS) and Stability Control .

No GO to A3

A3 CHECK FOR TBM (TRAILER BRAKE CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)

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

Does the TBM communicate with the diagnostic scan tool?

Yes	If there are Diagnostic Trouble Codes (DTCs) in the TBM, DIAGNOSE all TBM Diagnostic Trouble Codes (DTCs). GO to DTC Chart: Trailer Brake Control Module (TBM) . If there are no Diagnostic Trouble Codes (DTCs) in the TBM, GO to A4

No	DIAGNOSE the TBM does not communicate with the diagnostic scan tool. REFER to: Communications Network .

A4 CHECK THE BCM (BODY CONTROL MODULE) BRAKE SWITCH 2 (BOO_2) PID (PARAMETER IDENTIFICATION)
- Using a diagnostic scan tool, monitor the BCM BOO_2 PID while pressing and releasing the brake pedal.
Does the BOO_2 PID display ON with the brake pedal pressed and OFF with the brake pedal released?

Yes GO to A5

No DIAGNOSE the vehicle stoplamps. REFER to: Stoplamps .

A5 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) BRAKE SWITCH (BRAKE_SW) PID (PARAMETER IDENTIFICATION)
- Using a diagnostic scan tool, monitor the TBM BRAKE_SW PID while pressing and releasing the brake pedal.
Does the BRAKE_SW PID display ON with the brake pedal pressed and OFF with the brake pedal released?

Yes GO to A6

No DIAGNOSE the BPP (stoplamp) switch. REFER to: Stoplamps .

A6 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) OUTPUT

NOTE: Battery voltage must be greater than 10 volts.

Ignition ON.

NOTE: If the manual slider switch is held to the full left position for more than 5 minutes, the TBM automatically shuts down.

NOTE: Do not apply the brake pedal during this test.

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

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 TBM is operating correctly. SEND the trailer to an authorized camper/trailer repair center.

GO to A7

A7 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) PWM (PULSE WIDTH MODULATION) OUTPUT CIRCUIT FOR A SHORT TO GROUND

Ignition OFF.

Disconnect TBM C2142 .

Measure:

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

Is the resistance greater than 10, 000 ohms?

Yes

GO to A8

No	REPAIR the circuit.

A8 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) PWM (PULSE WIDTH MODULATION) OUTPUT CIRCUIT FOR AN OPEN

Measure:

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

Is the resistance less than 3 ohms?

Yes

GO to A9

No	REPAIR the circuit.

A9 VERIFY ALL WIRING CONNECTIONS
- Disconnect BCM .
- Disconnect all in-line electrical connectors between the TBM and the BCM.
- Using a good light source, inspect all disconnected electrical connectors for the following:
  - corrosion - install new connector or terminal and clean the module pins
  - damaged or bent pins - install new terminals or pins
  - pushed-out pins - install new pins as necessary
  - spread terminals - install new terminals as necessary
Are the connectors free of corrosion, damaged pins, bent pins, pushed-out pins and spread terminals?

Yes GO to A10

No REPAIR the affected connectors or terminals. Refer to Connector Repair Procedures for schematic and connector information.

A10 CHECK FOR CORRECT TBM (TRAILER BRAKE CONTROL MODULE) OPERATION

Connect all in-line electrical connectors between the TBM and the BCM. Make sure they seat and latch correctly.

Connect BCM C2280A . Make sure it seats and latches correctly.

Connect TBM C2142 . 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 Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW the TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new TBM. REFER to: Trailer Brake Control Module (TBM) .

No	The condition causing the concern is not present at this time. The concern is intermittent and may have been caused by a loose or corroded connector, low battery voltage or an excessive load on the HS-CAN1 or HS-CAN2.