2004 Tahoe Tow Package Wiring

[rwag1945]

I have a 2004 Chevy Tahoe, which apparently has a wiring harness problem.
I have two trailers, both with new wiring harnesses and light assemblies.

ALL Tahoe lights work fine without a trailer connected.
Trailers have good grounds.

The Tahoe plug at the back tests “good” on all connections UNTIL the trailer is plugged in. Then the lights go crazy.
The Tahoe ground then tests “hot”
Tahoe lights: none on trailer
Brakes lights: none on trailer
Left Directional: good on trailer and Tahoe
Right Directional: none on trailer; Tahoe works, but both tail lights come on
Brake & left directional: Trailer has left directional; no brakes; Tahoe ok
Brake & right directional: Trailer has LEFT directional; no brakes; Tahoe ok
Lights & left directional: Trailer has left directional; no tail lights; Tahoe ok
Lights & right directional: Trailer has no lights; Tahoe has tail lights, but right directional stays on and does not blink

Both trailers have the same performance.
The Tahoe has a 7 way plug and uses an adapter to go from 7 to 4 for my trailers. The wiring has never been damaged or under water, and has worked fine for five years.
Can it be the right tail light module on the Tahoe? Wiring harness?

[F E Knucklebuster]

Both trailers have the same performance.
The Tahoe has a 7 way plug and uses an adapter to go from 7 to 4 for my trailers. The wiring has never been damaged or under water, and has worked fine for five years.

A thought.

The one thing that they all have in common when plugged in(do not work correctly) but don't share when unplugged(work correctly) is your adapter.

Have you checked it or swapped it out to test it?

[rwag1945]

YES, i HAVE TRIED 3 DIFFERENT NEW ADAPTERS. THANKS

[F E Knucklebuster]

I know how aggravating these things can be. I chased a phantom light problem on a Montana that ended up being a poor factory rear light harness.

Good info here - http://www.rofb.net/faq/faq_trailerwiring.htm

Since your truck is and has been working fine without the trailer hooked up, I would suspect the trailer(s) - since you said they both have a new harness. Bad ground - nicked wire - mixed wire?

Any chance you could hook up your trailer to another vehicle? If you have the same result you would know it's the trailers - if it works fine you have isolated it to your truck.

Good luck - these things are always no fun.