TRAILER WIRING ?
 

I have a 1991 steel bed 18' trailer. I bought it brand new.
It sits in my shed all year with the mice. I took it out a couple months ago to tow my new tractor. And noticed the trailer lights not working. I found several chewed wires and repaired them.
ALL the lights are working properly, running, turn and stop and they are bright.
But when I hook it up tp my2017 Silverado I get a ding,ding,ding and a message on the dash "check trailer wiring" ding,ding,ding.
What's going on ?

If your truck has OEM trailer hookup it might be expecting to see brakes. There is also a different standard for plugs now I think .... something like seven wire vs six wire ... I forget.

Have you towed the trailer before with this truck and lights work?

My first clueless wild guess would be the trailer has standard brake/turn and the truck has seperate brake/turn.

Clay

I’m by no means an expert, but did have trailer light issues recently with my 2011 Silverado.
Did you check the fuses? I figured my trailer lights would simply run through the fuses for the trucks tail/brake lights, not so. The trailer wiring has its own fuses separate from the truck lights. I never knew that, and made an easy fix.

It's normally a ground issue.
 

From google:

Why does my truck keep saying check trailer wiring?

This condition is most likely caused by insufficient trailer grounding and the trailer ground wiring will need to be repaired and/or upgraded. 2. These concerns could be caused by a poor connection at the 7-way trailer connector. It could be either the truck and/or trailer side of the connector.

Several other sites pointed out chewed-on wiring causing the bad connection.

NHTSA says
NOTE: It is normal for the DIC to display "Check Trailer Wiring" when the trailer is disconnected from the truck while the ignition is in the run position. - Check Trailer Wiring message with DTC C1114 (NO Service Trailer Brake message). ... This symptom is caused by a short to power on circuit 47 or a poor trailer ground.

Good luck!

I had the same message on 2 newer 2021 GMC diesel trucks. Same trailer. Wire on brakes shorted to ground and I found blown fuse for trailer brakes on both trucks. Repaired wire installed new fuses everything ok.

yes. Fuses all good, how else would all the lights work ?
I agree with the ground issue, gotta look.

Ground is secure at the junction box but from there all wires go inside the box frame. 30 years mite be time to rewire the whole trailer ?
THANKS TO THE MOD WHO CORRECTED MY MISPELLED (WIREING). ;)

When I built my open trailer 35 yrs ago I ran the wires through metal conduit. Left and right wiring separate till they junction at front. So mice can only get at wiring in the front.