PINPOINT TEST AC : The Trailer Module (TRM) Does Not Respond To The Diagnostic Scan Tool

WARNING: This page is about a different car, the 2017 Lincoln Navigator and 2017 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery, Mounting and Cables .

AC1 CHECK THE TRAILER MODULE (TRM) VOLTAGE SUPPLY CIRCUIT FOR AN OPEN

Ignition OFF.

Disconnect: Trailer Module (TRM) C2498A .

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2498A-1	Courtesy of FORD MOTOR COMPANY	Ground
C2498A-2	Courtesy of FORD MOTOR COMPANY	Ground

Are the voltages greater than 11 volts?

Yes	GO to AC2.
No	VERIFY BJB fuses 21 (30A) or 48 (40A) is OK. If OK, REPAIR the circuit. If not OK, REFER to the OEM Electrical Wiring Diagram Introduction to identify the possible causes of the circuit short.

AC2 CHECK THE TRAILER MODULE (TRM) GROUND CIRCUIT FOR AN OPEN

Ignition OFF.

Disconnect: Trailer Module (TRM) C2498B .

Disconnect: Negative Battery Cable.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2498B-1	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance less than 3 ohms?

Yes	GO to AC3.
No	REPAIR the circuit.

AC3 CHECK THE MS-CAN CIRCUITS BETWEEN THE TRAILER MODULE (TRM) AND THE DLC FOR AN OPEN

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2498B-3	Courtesy of FORD MOTOR COMPANY	C251-3
C2498B-2	Courtesy of FORD MOTOR COMPANY	C251-11

Are the resistances less than 3 ohms?

Yes	CONNECT the negative battery cable. GO to AC4.
No	REPAIR the circuit in question.

AC4 CHECK FOR CORRECT TRAILER MODULE (TRM) OPERATION

Ignition OFF.

Disconnect and inspect the Trailer Module (TRM) connector and related in-line connectors.

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

Reconnect the Trailer Module (TRM) connector and related in-line connectors. Make sure they seat and latch correctly.

Operate the system and determine the concern is still present.

Is the concern still present?

Yes	CHECK OASIS for any applicable TSBs. If a TSB DISCONTINUE this test and FOLLOW TSB instructions. If no TSBs address this concern, INSTALL a new TRM. REFER to Exterior Lighting .
No	The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.