Obscure Trailer Light Problem.

[tjr508]

I have a factory tow kit and my right turn signal works, but not my right brake light on my trailer. The left brake and turn work fine. There are no other problems. The turn and brake lights are fused together so it is not a fuse.

 

My guess is that there is some module that splices the brake and turn signals together (before the fuse box) and that this module is malfunctioning. Any pointers on where I can find this. Any part #'s?

[MustGoFaster]

check the basics first - check the bulb and socket on the trailer

a buddy had a bizzare light problem with his jeep - turned out to be the wrong bulb in the trailer socket

[tjr508]

Basics are checked. Checked with DMM. The flasher and brake are on the same line anyhow. Has done the same thing on 3 separate trailers as well.

[MustGoFaster]

bummer - I take it that the lights operate properly when the trailer is disconnected? or do the tail lights on the truck malfunction as well when the trailer is connected?

is the trailer a 4-wire unit? if so perhaps your adapter crapped out?

 

if the brake and turn lights on the truck all work correctly and the adapter is good, then I woudl probe the wires going into the back of the stock connector and see if they are powered at the appropriate times.

 

long shot but maybe water got into the back of the stock harness and crapped out a wire or a terminal.

[tjr508]

Sorry again. All tail lights on the truck itself work fine and always have with or whthout the trailer. The harness has been checked too. Everything is fine, but there is just no brake signal getting sent to the right side. The truck must have a coupler though to couple the turn/brake to the same wire. I think I need to find that coupler.

 

I have checked this as far up as the fuse box. There is a turn signal working on the right side just fine, but no brake, so the problem lies before the fuse box. As before, the lights on the truck are fine and the lights on the left side of the trailer are fine too.

[asilverblazer]

If I had the schematics on an 03 I'd look it up, its weird. But I think you are on the right track. You can start at the brake light switch and trace those wires back, I'd bet its the BCM.

[Reeper27]

Check Fuses under the hood, If I remember correctly each circuit on the trailer harness has a seapret fuse, I know it sounds wired cause its the brake lights, but you just never know, and I don't have access to my truck to see for myself.

[lost_in_alabama]

Check the ground. I've seen a bad ground cause very weird light problems.

[383S-10]

Yeah a crustry ground will that I can surely attest to that. Had to redo mine had a similar problem. I bought a test light set from Wal mart that helped me out less that 8 bucks. I started from the plug on the vehicle and found that I wasnt getting a strong connection out of it. Traced it back alternate ground on hitch receiver......bolt was crusty rusty. Had a electrician redo wire & hog ring too a new ground spot filed, drilled pilot hole & used a hex head bolt that cut into the metal of the hitch receiver. Hope you find your gremlin, later.

[rak]

Help! I have searched forum topics and have not found anything regarding my situation.

 

I have a 2005 GMC Yukon with the tow package. I was really stupid and was replacing a bulb with the lights on and while pulling the bulb, I must have shorted something because now all tralier lights are out. It was one of those deals where the glass twisted from the base of the bulb. I checked the TLR PARK 15 amp fuse under the hood to find that the fuse was blown. Great. I replace the fuse with confidence to find that the trailer lights still don't work. I went back to the TLR PARK fuse to find that it blew again. I checked the fixtures on the car hauler trailer and they were fine. (works great on my neighbors truck harness).

On my 2000 tahoe, I remember having to bring it in to the shop and they said there was an in-line harness fuse that had blown. Do I have one on the Yukon?

So...

Question 1: why is it now that I am blowing the 15 Amp TLR PARK fuse immediately?

Question 2: is there an in-line harness fuse? If so where is it and would this be causing me to blow the TLR PARK fuse?

Question 3: Is this TLR PARK fuse the only one under the hood? or are there other fuses I should be looking for?

 

The owners manual is void of any detail regarding the wiring harness fuse set up.

 

All the lights on the truck itself are working fine. I know it was probably not a good think to have power to the lights when changing the bulb, but it seems very harsh that by doing this, I have completely messed up my factory trailer wiring harness.

 

Please help and advise..

 

Thank you very much!

 

Roger

[asilverblazer]

Do the trailer plug and truck plug match functions?

[rak]

yup. The connector maps perfectly to the functions on the truck.

 

So, here's the deal. I started from scratch again. Replaced the 15a fuse. checked all the light operation on my neighbors truck -- All worked great.

 

PLugged the trailer into my truck, anf vuola... everything works fine! Both trailers. My utility and car hauler.

 

I don't what the heck happened but it is all working again. I am going to go through the trailers to be sure there is no short someplace.

 

Thanks for your reply!

 

Roger