taillight problems

[Shinebox]

Looked all over the site don't see this anywhere. I have a stock 2010 Tahoe. First the blinker started to go fast figured it was a burned out bulb. Nope. Now that only happens every now and then. But now when hitting the brake the reverse lights come on with the brake lights?? I have never seen this on a Tahoe before, I see it all the time on the Express vans. Any one else have this happen? If so what was wrong with it.

Naturally it just out of warranty

 

[Dimond9035]

Looked all over the site don't see this anywhere. I have a stock 2010 Tahoe. First the blinker started to go fast figured it was a burned out bulb. Nope. Now that only happens every now and then. But now when hitting the brake the reverse lights come on with the brake lights?? I have never seen this on a Tahoe before, I see it all the time on the Express vans. Any one else have this happen? If so what was wrong with it.

Naturally it just out of warranty

Mine is doing the same thing I've searched and searched online and can't seem to find anything

 

[papaman]

this happened to me once as well. it was very irritating! i took off the passenger tail light assembly, tested the bulbs with an ohm meter, then reseated all the bulbs, and re-assembled them into the housing. the issue for me magically disappeared after that, and has not returned for the last 7 months. i need to go knock on wood now....

 

[papaman]

so after many months, this issue happened to me again this past weekend. i think i might have found the issue and fixed it this time.

the issue came back after i went over a succession of ~10 speed bumps at low speed. anytime i put my blinker on (either direction) and stepped on the brakes, the blinker work at twice the normal blink rate. when not in the vehicle, and you press the unlock button on the key fob, the three bulbs in the passenger side tail light are significantly dimmer than the driver side.

the bulbs were getting some voltage since i could see the filaments in the bulbs were glowing very dimly. i pulled the tail light out and checked each bulb with an ohm meter, and they tested fine. led me to believe there was a short or bad connection. i followed the wire loom from the back of the assembly, and it runs behind the bumper and above the muffler to a connector. i disconnected the connector and a lot of dust/dirt came pouring out of the loom and the connector. i cleaned the prongs in the connector as best i could, reassembled everything, and the lights began to work properly again.

this worked for me. maybe it will help someone else.

 

[Jay215]

I am having the same issues in my 2011 GMC Yukon XL. Checked all grounds and cleaned them up. cleaned up the connector as mentioned above. Disconnected the trailer brake controller. Nothing.
What is irritating is the problem is intermittent sometimes lights work normal. I am at a loss for what the prob could be. Any help would be appreciated.
Might need to take it to the dealership.

 

[papaman]

I am having the same issues in my 2011 GMC Yukon XL. Checked all grounds and cleaned them up. cleaned up the connector as mentioned above. Disconnected the trailer brake controller. Nothing.
What is irritating is the problem is intermittent sometimes lights work normal. I am at a loss for what the prob could be. Any help would be appreciated.
Might need to take it to the dealership.

jay215 - did you happen to take your truck to the dealer for diagnosis? the issue keeps coming and going for me, and was wondering if anyone had discovered the root cause yet... for me, it seems to start back up after i go over a speed bump too quick, then it just goes away on it's own.

 

[papaman]

woohoo! i found the root cause for my issue!

this is the issue i was having:

for those that may search in the future, here's what i did/checked:

verified that fuse number 8 below and left of the instrument cluster was good.
use ohm meter to test each of the 4 bulbs in the rear taillight assembly to verify they were good.
checked the turn signal bulb in the front right corner of the vehicle and verified it was good.
checked the voltage in the bulb sockets, and noticed the readings wavered when i wiggled the harness.
that prompted me to check the connector that bundles all of the bulb sockets under the truck:

this is the issue. this harness is under the vehicle in the rear passenger corner above the muffler. when i moved the wires circled in red, all the lights would begin to work properly. when i moved the wires around even more, i noticed the issue would come and go. so it looks like i need to really check each pin and make sure there are proper contacts in the harness.

hope this helps!