Brake lights

[Dleach]

I have a 2020 1500 I hooked trailer up know passenger rear brake light won’t turn off even with key out pull the trailer tow fuse it turns off.

 

[Fatherof3]

Sounds like a short somewhere . Somebody with a lot more experience on this will chime in .

 

[Richard320]

It sure sounds like a lousy ground connection somewhere, so the juice that should be going to ground is instead running through the right trailer stop/turn and feeding back through the truck light to find a ground there.

 

[Dleach]

Any idea we’re to start I have crawled all over it

 

[Dleach]

I disconnected the trailer brake module didn’t change.there is a plug into a module back left hand side there is power in one pin constantly so I assume it’s the one going to brake light so I assume it’s up the front somewhere doesn’t seem to be anything braking off the harness right up to the front but goes into a big harness and loose it from there.

 

[Richard320]

It could be the ground connection on the trailer.

Step one, does everything work good without the trailer plugged in?
Step two does anything else behave strange when the trailer is plugged in? Try everything. I once wired up a buddy's car and trailer, and individually everything worked great, but as soon as he turned on the turn signal with the headlights on, things went nuts. Clearance lights started flashing, but only on one side. Stuff like that. And it was the ground on the trailer frame.

Step three, drop the spare and study all the wiring. Look for wires breaking out of the rear harnesses that might go to ground. Maybe even pull the rear light and see if there's a ground somewhere there. Then go looking along the edge of the engine compartment at the body grounds leading to the negative battery cable.

 

[Dleach]

The left one stays on all the time trailer is unplugged.and it’s still on even with vehicle off I have checked all these things I can notice anything.if I pull the tow fuse it’s called it goes out but have no brake lights then at all.I have checked all that can’t find anything out ordinary.tried unplugging the tow module still nothing.

 

[Richard320]

The left one stays on all the time trailer is unplugged.and it’s still on even with vehicle off I have checked all these things I can notice anything.if I pull the tow fuse it’s called it goes out but have no brake lights then at all.I have checked all that can’t find anything out ordinary.tried unplugging the tow module still nothing.

Does the right one work?

Because if the trailer brake gets activated, the stop lamps are supposed to come on. Could be that the trailer brake unit is powered up but the right bulb is out.

 

[Dleach]

The right one is working as normal.but I disconnected the trailer brake module should rule that out from what I read you can get the module and controller later so brake lights must work with out them in.

 

[Richard320]

Lacking a wiring diagram, I can't even guess what now. Do the brake lights come off the pedal, or does the BCM control the lights? I don't know.

 

[Dleach]

The one on the roof works off the pedal and it’s working fine that’s all I can work out. And the left and right brake light is on a separate wire or they would be both on

 

[Dleach]

I believe it’s this module there is only one wire with constant power in it which I believe is aux power for trailer plug so my guess is there is something fried in here or it’s between there and trailer plug