Pinpoint Test E: The Message Center Displays A False Trailer Disconnected Message When A Trailer Is Connected To The Vehicle

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

Refer to TRAILER/CAMPER ADAPTER for schematic and connector information.
Normal Operation and Fault Conditions

The TRM receives information from the ABS module over the HS-CAN. If there is a concern in the ABS module preventing this information from being sent to the TRM, the TRM enters a limited operating mode.

Both the TBM and the TRM use trailer connectivity to monitor system. The TBM looks at the trailer brake circuit and the TRM looks at the lighting circuit. For TRM issues refer to REFER to: Trailer Lamps . .

REFER to: Auxiliary Brake System - System Operation and Component Description .

Possible Sources
- Wiring, terminals or connectors
- TRM
Visual Inspection and Pre-checks
- Trailer without trailer brakes will not be detected in message center.
- Electric over hydraulic type trailer brakes disables the inductance test from TRM, make sure the Trailer Brake Type in the message center matches the customers trailer.

E1 CHECK TRM (TRAILER MODULE) DTC (DIAGNOSTIC TROUBLE CODE)

NOTE: The TRM is a combined TBM and Trailer Lighting Module.
- Ignition ON.
- Using a diagnostic scan tool, carry out the TBM self-test.
Are any Diagnostic Trouble Codes (DTCs) present in the TBM?

Yes DIAGNOSE all TBM Diagnostic Trouble Codes (DTCs).

No GO to E2

E2 CHECK MESSAGE CENTER TOWING STATUS

NOTE: Before performing any testing check customers message center setting's in TOWING . Set TRAILER BRAKE TYPE to Electric or misdiagnosis could occur.

NOTE: Unless instructed otherwise, carry out all pinpoint tests without a trailer or emulator connected to the vehicle.
- Ignition ON.
  NOTE: Observe message center when turning ignition to ON, message only displayed for limited amount of time.
Does the vehicle indicate No Trailer Connected in the message center?

Yes GO to E3

No GO to E4

E3 CHECK TBM (TRAILER BRAKE CONTROL MODULE) TRAILER CONSTAT PID STATUS

NOTE: Before performing any testing check customers message center setting's in TOWING . Set TRAILER BRAKE TYPE to Electric or misdiagnosis could occur.

NOTE: Unless instructed otherwise, carry out all pinpoint tests without a trailer or emulator connected to the vehicle.
- Ignition ON.
- Using a diagnostic scan tool, access the TBM PID's (parameter identifications).
- Using a diagnostic scan tool,
  Access the TBM and monitor the CONSTATPID
- Apply the vehicle brakes for at least 2 seconds.
Does the CONSTAT PID display False?

Yes GO to E5

No GO to E4

E4 CHECK TRM (TRAILER MODULE) TRAILER ON PID STATUS

Using a diagnostic scan tool, access the TRM PID's (parameter identifications).

Using a diagnostic scan tool,
Access the TRM and monitor the TRAILER_CONPID

Apply the vehicle brakes for at least 2 seconds.

Does the TRAILER_CON PID display False?

Yes	The condition causing the concern is not present at this time. The concern is intermittent and may have been caused by improper wiring on the trailer, a loose or corroded 7-pin connector or improper messages on the HS-CAN3.

No	REFER to: Trailer Lamps .

E5 CHECK THE 7 PIN TRAILER TOW CONNECTOR TRAILER BRAKES CIRCUIT FOR AN OPEN

Ignition OFF.

Disconnect TRM C2498C.

NOTE: C4099 connects to the back of the 7 way trailer tow connector.

Disconnect C4099.

Measure:

Rear Bumper

Positive Lead	Measurement / Action	Negative Lead
C2498C-14	Courtesy of FORD MOTOR COMPANY	C4099-3

Is the resistance less than 3 ohms?

Yes

GO to E6

No	REPAIR the circuit.

E6 CHECK THE 7 PIN TRAILER TOW CONNECTOR TRAILER BRAKES CIRCUIT FOR A SHORT TO GROUND

Measure:

Rear Bumper

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

Is the resistance greater than 10, 000 ohms?

Yes

GO to E7

No	REPAIR the circuit.

E7 CHECK THE 7 PIN TRAILER TOW CONNECTOR TRAILER BRAKES CIRCUIT FOR A SHORT TO VOLTAGE

Ignition ON.

Measure:

Rear Bumper

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

Is any voltage present?

Yes	REPAIR the circuit.

GO to E8

E8 VERIFY ALL WIRING CONNECTIONS

Disconnect TRM and related in-line connectors.

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 E9

No	REPAIR the affected connectors or terminals. Refer to OEM CONNECTOR REPAIR PROCEDURES for schematic and connector information.

E9 CHECK FOR CORRECT TRM (TRAILER MODULE) OPERATION

Connect all in-line electrical connectors. Make sure they seat and latch correctly.

Connect TRM C2498C. 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 TRM module. REFER to: Trailer Module (TRM) .

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-CAN3.