2004 Chevy tahoe Wiring Problem

**rwag1945** · 09-05-2009, 12:23 PM

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 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?

**canislupis69** · 09-05-2009, 10:52 PM

Welcome to the site...you will get more responses if you post under the Tech section.

**tattooed4life** · 09-05-2009, 11:15 PM

Originally Posted by 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 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?

Is it a 4-way or a 7-way plug on the back of your tahoe? If it's a 4-way plug those can heat up and over time they start to melt the rubber and the wires short themselves. The only fix for this is to replace the whole harness. (simple plug in play repair) If its a 7-way plug, take the housing apart and inspect all the connections for corrosion or loose wires. They have a tendancy to collect moisture. Remove them and clean up with sandpaper or a file and some electronic parts cleaner. When I did mine I also put a little dielectric grease on each connection to ward off the moisture. Good luck, hopes that helps. and Welcome to the site!

**adampaul1964** · 09-06-2009, 01:23 AM

Welcome to the site!

**Jimmiee** · 09-06-2009, 07:51 AM

This is a very common problem. Electricity is lazy and seeks the easiest path to ground. If you find voltage on the ground and it tests "hot" then you have found the short. High resistance in the plug is the most likely cause. Take the trailer plug apart and clean the wires. If you want a better fix for this problem tin the tips of the wires with solder before you re-assemble the plug.