We were 25 miles away from our second campground on a 3 day 1000 mile trip when the message center on my 09 F250 indicated "Trailer Disconnected". The trailer running lights were still on and braking felt normal. When we got to the Crossville,TN KOA I checked the trailer plug and it appeared to be properly seated. On restarting my truck the message center indicated "Trailer Connected". Some type of intermittent apparently. Any idea what connection the factory trailer electronics uses to determine trailer connection?

Your truck is seeing an intermittent connection of the trailer brakes. You need to inspect the trailer plug and brake wiring all the way to the magnets. That includes any wires inside the axles.

Lynnmor wrote:Your truck is seeing an intermittent connection of the trailer brakes. You need to inspect the trailer plug and brake wiring all the way to the magnets. That includes any wires inside the axles.So you are saying the Ford trailer system is monitoring the brake circuit only to determine connectivity? Is that continuous or only when brakes are applied and the system monitors current draw?

dclark1946 wrote:Lynnmor wrote:Your truck is seeing an intermittent connection of the trailer brakes. You need to inspect the trailer plug and brake wiring all the way to the magnets. That includes any wires inside the axles.So you are saying the Ford trailer system is monitoring the brake circuit only to determine connectivity? Is that continuous or only when brakes are applied and the system monitors current draw?When there is continuity, (wiring is connected to ground) thru the brake magnets, the truck determines there is a trailer connected and will give the trailer connected notice. When that continuity is broken with the engine on, by a bad connection or other wiring fault, you will get the disconnected notice. This repeats each time the engine is restarted. Of course if the trailer disconnects either by operator or fault, the truck will not give any notices when restarted.

I had the same problem on my truck. It turned out to be the brake wires inside the axle tubes had worn through in a spot and caused very intermittent issues like this

I had the same message on my truck. It was caused by the brake wiring on the trailer being cut by up/down axle movement. The warning initially would show on rough road conditions. The warning became permanent when the wires were cut. Spliced the wires during a rest stop. No more disconnect warnings.

F250 Trailer Disconnected Message | Good Sam Community

Lynnmor
Explorer
Aug 06, 2017
dclark1946 wrote:
Lynnmor wrote:
Your truck is seeing an intermittent connection of the trailer brakes. You need to inspect the trailer plug and brake wiring all the way to the magnets. That includes any wires inside the axles.

So you are saying the Ford trailer system is monitoring the brake circuit only to determine connectivity? Is that continuous or only when brakes are applied and the system monitors current draw?

When there is continuity, (wiring is connected to ground) thru the brake magnets, the truck determines there is a trailer connected and will give the trailer connected notice. When that continuity is broken with the engine on, by a bad connection or other wiring fault, you will get the disconnected notice. This repeats each time the engine is restarted. Of course if the trailer disconnects either by operator or fault, the truck will not give any notices when restarted.
dclark1946
Explorer
Aug 06, 2017
Lynnmor wrote:
Your truck is seeing an intermittent connection of the trailer brakes. You need to inspect the trailer plug and brake wiring all the way to the magnets. That includes any wires inside the axles.

So you are saying the Ford trailer system is monitoring the brake circuit only to determine connectivity? Is that continuous or only when brakes are applied and the system monitors current draw?
Lynnmor
Explorer
Aug 06, 2017
Your truck is seeing an intermittent connection of the trailer brakes. You need to inspect the trailer plug and brake wiring all the way to the magnets. That includes any wires inside the axles.

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F250 Trailer Disconnected Message

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