Tail Light Problems

[rizzy71]

I have a 1997 GMC Yukon that is having tail light problems. When the lights are turned on I do not have taillights or brake lights. If the switch is off the brake lights work fine. When the turn signal is on, the opposite side blinks too, but its very dim. I have replaced everything that I can think of or that I have found when searching that might be the problem. All front lights work properly.

REPLACED:

All exterior light bulbs

All fuses and relays that are for lights

Rear circuit boards

Brake switch

Grounds for the tail lights

Three different main light switches

Any help or other ideas are very appreciated.

[reedal]

I just recently fixed this issue for my uncle's OBS Silverado. Unfortunately, one of the issues was the ground you said you replaced. On the rear most center of the frame. Do you have a trailer harness? That was also causing issue as the wiring was old and cracked and grounding out.

[audiofanaticz]

Has the vehicle always had this issue, or has it just started happening?

Im with reedal on trailer wiring either being shorted out from exposed wires, or not installed correctly.

You may have to crawl under the back to see if you have it wired for a trailer, sometimes people tuck them up pretty well.

[reedal]

Another question, does it affect your dashboard and license plate lighting at all, or just the rear tail lights/brake lights?

[rizzy71]

I just recently fixed this issue for my uncle's OBS Silverado. Unfortunately, one of the issues was the ground you said you replaced. On the rear most center of the frame. Do you have a trailer harness? That was also causing issue as the wiring was old and cracked and grounding out.

I unhooked the tailer harness back last summer because the wires were starting to crack. I just unhooked it at the T.

Has the vehicle always had this issue, or has it just started happening?

Im with reedal on trailer wiring either being shorted out from exposed wires, or not installed correctly.

You may have to crawl under the back to see if you have it wired for a trailer, sometimes people tuck them up pretty well.

I unhooked it back last summer and the problems just started a couple weeks ago.

Another question, does it affect your dashboard and license plate lighting at all, or just the rear tail lights/brake lights?

It's only in the tail lights and brake lights.

[ShadeTreeMechanic]

Sounds like you have a floating ground. I have seen this many times on trailers. Check it with a test light.