Pinpoint Test B : The Trailer Brakes Are Always Engaged

WARNING: This page is about a different car, the 2018 Lincoln Navigator. 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.

B1 CHECK FOR BCM (BODY CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)
- Ignition ON.
- Using a diagnostic scan tool, carry out the BCM self-test.
Are there 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 B2

B2 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 there 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 B3

B3 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 the DTC Chart: TBM.If there are no Diagnostic Trouble Codes (DTCs) in the TBM, GO to B4

No	DIAGNOSE the TBM does not communicate with the diagnostic scan tool. REFER to: MODULE COMMUNICATIONS NETWORK (2 OF 2) .

B4 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 B5

No DIAGNOSE the vehicle stoplamps. REFER to: STOPLAMPS .

B5 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 B8

No GO to B6

B6 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) BPP (BRAKE PEDAL POSITION) SWITCH INPUT CIRCUIT FOR A SHORT TO VOLTAGE

Ignition OFF.

Disconnect TBM C2142 .

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2142-12	Courtesy of FORD MOTOR COMPANY	Ground

Is any voltage present?

Yes

GO to B7

GO to B10

B7 ISOLATE THE BCM (BODY CONTROL MODULE)

Remove BCM fuse 4 (5A).

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2142-12	Courtesy of FORD MOTOR COMPANY	Ground

Is any voltage present?

Yes	REPAIR the circuit.

No	INSTALL a new BCM. BCM guided routine is not applicable for this vehicle and market. Replace the component that was faulted through service information diagnosis.

B8 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) OUTPUT

NOTE: Every 4 seconds a voltage pulse is output by the TBM as a trailer connectivity test.

Ignition ON.

Make sure the brake pedal is not being pressed and the manual slider switch is not being applied.

Measure:

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

Is a steady voltage present?

Yes

GO to B9

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

B9 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) PWM (PULSE WIDTH MODULATION) OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE

Ignition OFF.

Disconnect TBM C2142 .

Ignition ON.

Measure:

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

Is any voltage present?

Yes	REPAIR the circuit.

GO to B10

B10 VERIFY ALL WIRING CONNECTIONS

Ignition OFF.

Disconnect BCM C2280A .

Using a good light source, inspect TBM C2142 and BCM C2280A 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 B11

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

B11 CHECK FOR CORRECT TBM (TRAILER BRAKE CONTROL MODULE) OPERATION

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 service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions.If no service articles address this concern, INSTALL a new TBM module. REFER to:Trailer Brake Control Module (TBM) .

No	The condition that caused 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.