help with lighting/electrical/fuse issue?

[Rokmonanoff]

Hello all,
I have an interesting glitch going on with my 06 Denali. We bought this vehicle used about a month ago. My wife said it happened within a couple of days of buying it, but we couldn't get it to duplicate. It has come back now for the last couple of days. I will explain what is going on.

Without turning lights on:
-When I turn on the turn signals, they work fine until I depress the brakes. -The blinker then hesitates and continues functioning

With lights on:
-When I turn on the headlights, all headlights, taillights, and brake lights work fine initially.
-When I turn on the turn signals, two things happen
----they signal at a faster rate (like trying to tell me one is out)
----the mirror signal on the opposite side lights up halfway in addition to the mirror for the signal that is intended lighting up

Additionally, when the lights are turned on...
-When I depressed the brake:
----the tail lights quit being illuminated
----the brake lights do not illuminate
----the 3rd brake light does illuminate
----the turn signals quit flashing, but ...
=====the mirror signals fully illuminate and hold while braking (like the vehicle is trying to compensate for no brake lights)
=====the turn signal arrows on the dash illuminate and hold while braking as well

My initial thoughts were:
-light out somewhere
-fuse
-possible short in the wiring somewhere

I read through a couple of posts on lighting issues, and checked bulbs and fuses, but have not found anything amiss. It's possible that I have missed something. I will recheck all of the bulbs and fuses. If anyone has a specific area to target, that would be awesome.

If you have other possible reasons for this issue, I am all ears. If I can't figure it out in the next day or so, I'll take it to the shop to have them chase down the issue.

Otherwise... WTF?

Thanks,

Rok

 

[chauncey0337]

I've seen a couple situations similar to yours. The problem was a bad ground for the tail lights. I think I recall a ground under the truck, in the rear. Might check there.

 

[delta579]

I agree sounds like a bad ground. Typical in that it's searching for a ground through any unused circuit.

 

[Rokmonanoff]

Thanks for the lead on this. I will check out this evening and let you know how it goes.

Rok

 

[chauncey0337]

The ground I was speaking of is on the driver's side, to the rear of the truck. It's a braided ground to the chassis. disconnect it and clean the contact point.

 

[ScottyBoy]

I have also seen this happen when someone added a 4 pin trailer plug and didn't wire it correctly, or put poor connections on it and one or more of the wires shorted to each other or to a ground.

 

[afpj]

Also might want to check condition of battery (with a load tester etc) and it's connections as a corollary to the above suggestions

 

[PlazaEJ]

If any of these haven't cured your problem, there's a junction block under the right rear fender. If it has gotten water/dirt/etc. inside, things can get weird. It's amazing what a small thing like a bad connection can do.

That being said, I'm betting a bad ground somewhere.

EJ

 

[Rokmonanoff]

So, I crawled under to looked at the wires where you guys directed (rear driver side). I couldn't find anything amiss. Wires were all without cracks. Contacts were clean. I cleaned again anyway. I couldn't find anything else worth paying attention to, and my electrical skills are limited.

I took it to the shop. It was the rear "lighting junction box" (correct description?). I never would have figured that out, and likely would have messed more up if I'd tried much else.

It's fixed now and running right.

Wife is happy again .

Thanks for the help.

Rok

 

[Rivieraracing]

Glad you got it fixed and posted up your results for others to learn from!!