Pinpoint Test A : All The Trailer Lamps Are Inoperative

WARNING: This page is about a different car, the 2018 Ford EcoSport. However, it is still accessible from the selected car via links, so may be relevant.

A1 CHECK THE TRAILER TOW CONNECTOR FOR GROUND

Ignition OFF.

Disconnect: Trailer.

Ignition ON.

Place the headlamp switch in the PARKING LAMPS position..

Measure:

Positive Lead	Measurement / Action	Negative Lead
Trailer tow connector parking lamps circuit	Courtesy of FORD MOTOR COMPANY	Trailer tow connector ground circuit

Is the voltage greater than 11 volts?

Yes	The vehicle is operating correctly. SEND the trailer to an authorized camper/trailer repair facility.

GO to A2

A2 CHECK THE TRAILER TOW CONNECTOR GROUND CIRCUIT FOR AN OPEN

Ignition OFF.

Measure:

Positive Lead	Measurement / Action	Negative Lead
Trailer tow connector ground circuit	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance less than 3 ohms?

Yes

GO to A3

No	REPAIR the circuit.

A3 CHECK FOR VOLTAGE TO THE TRM (TRAILER MODULE)

Disconnect: TRM C4397A.

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C4397A-1	Courtesy of FORD MOTOR COMPANY	Ground

Is the voltage greater than 11 volts?

Yes

GO to A4

No	VERIFY the BJB fuse 26 (20A) is OK. If OK, REPAIR the circuit. If not OK, REFER to the SYSTEM WIRING DIAGRAMS to identify the possible causes of the circuit short.

A4 CHECK THE TRM (TRAILER MODULE) GROUND

Ignition OFF.

Disconnect: TRM C4397B.

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C4397A-1	Courtesy of FORD MOTOR COMPANY	C4397B-1

Is the voltage greater than 11 volts?

Yes

GO to A5

No	REPAIR the circuit.

A5 CHECK FOR CORRECT TRM (TRAILER MODULE) OPERATION

Disconnect and inspect all 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 Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) 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.