Pinpoint Test A : All The Trailer Lamps Are Inoperative

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.

A1 CHECK THE TRAILER TOW GROUND CIRCUIT FOR CONTINUITY TO GROUND

Ignition OFF.

Disconnect: Trailer.

Disconnect: Negative Battery Cable.

Measure:

For 4-Pin Connector

Positive Lead	Measurement / Action	Negative Lead
4-Pin Connector, Pin 4	Courtesy of FORD MOTOR COMPANY	Ground

For 7-Pin Connector

Positive Lead	Measurement / Action	Negative Lead
7-Pin Connector, Pin 2	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance less than 3 ohms?

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

GO to A2

A2 CHECK THE TRAILER TOW GROUND CIRCUIT FOR AN OPEN

Disconnect: Trailer Tow C4099 .

Measure:

Positive Lead	Measurement / Action	Negative Lead
C4099-2	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance less than 3 ohms?

Yes	INSTALL a new trailer tow connector. TEST the system for normal operation.

No	REPAIR the circuit.