Pinpoint Test AF: The TRM (Trailer Module) Does Not Respond To The Diagnostic Scan Tool

Refer to Module Communications Network for schematic and connector information. Refer to Trailer/Camper Adapter for schematic and connector information.
Normal Operation and Fault Conditions

The TRM communicates on the MS-CAN.

Possible Sources
- Fuse
- Wiring, terminals and connector
- TRM
Visual Inspection and Pre-checks
- Verify BJB fuse 78 (40A) is OK.

AF1 CHECK THE TRM (TRAILER MODULE) VOLTAGE SUPPLY CIRCUIT FOR AN OPEN

Ignition OFF.

Disconnect: TRM C425A.

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C425A-1	Courtesy of FORD MOTOR COMPANY	Ground

Is the voltage greater than 11 volts?

Yes

GO to AF2

No	VERIFY BJB fuse 78 (40A) is OK. If OK, REPAIR the circuit. If not OK, REFER to OEM Electrical Wiring Diagram Introduction to identify the possible causes of the circuit short.

AF2 CHECK THE TRM (TRAILER MODULE) GROUND CIRCUIT FOR AN OPEN

Ignition OFF.

Disconnect: TRM C425B.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C425B-1	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance less than 3 ohms?

Yes

GO to AF3

No	REPAIR the circuit.

AF3 CHECK THE MS-CAN (MEDIUM SPEED-CONTROLLER AREA NETWORK) CIRCUITS BETWEEN THE TRM (TRAILER MODULE) AND THE GWM (GATEWAY MODULE A) FOR AN OPEN

Disconnect GWM C2431.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C425B-3	Courtesy of FORD MOTOR COMPANY	C2431-23
C425B-2	Courtesy of FORD MOTOR COMPANY	C2431-22

Are the resistances less than 3 ohms?

Yes	CONNECT the GWM, GO to AF4

No	REPAIR the circuit in question.

AF4 CHECK FOR CORRECT TRM (TRAILER MODULE) OPERATION

Ignition OFF.

Disconnect and inspect the TRM 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 TRM connectors. Make sure they seat and latch correctly.

Operate the system and determine if the concern is still present.

Is the concern still present?

Yes

CHECK OASIS for any applicable service articles: TSB, General Service Bulletin (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. REFER to: Trailer Module (TRM)

No	The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.