Tail light trouble

Greaser

Original poster
Member
Dec 30, 2012
4
I'm new, hoping one of you fine knowledgable people could help.
My 2003 trailblazer is having problems
The reverse lights blink when turn signals are on. The middle red lights come on when it's put in reverse and the stop lights are working properly.
This vehicle is stock and the only thing is it looks like the previous owner installed is Panother pig tail for some unknown reason.
I'm thinking the boards our bad but want to get some opinions before I buy something for nothing.

Thanks in advance
 

Blckshdw

Moderator
Nov 20, 2011
10,674
Tampa Bay Area, FL
Greaser said:
I'm new, hoping one of you fine knowledgable people could help.
My 2003 trailblazer is having problems
The reverse lights blink when turn signals are on. The middle red lights come on when it's put in reverse and the stop lights are working properly.
This vehicle is stock and the only thing is it looks like the previous owner installed is Panother pig tail for some unknown reason.
I'm thinking the boards our bad but want to get some opinions before I buy something for nothing.

Thanks in advance

I assume you mean that pigtail was installed on the tail light assembly that's functioning differently? It sounds like the wires for those 2 sockets are in the wrong place in their harness. How comfortable are you with wiring and taking harnesses apart? Looks like a simple swap is in order. :yes:
 

Greaser

Original poster
Member
Dec 30, 2012
4
Blckshdw said:
I assume you mean that pigtail was installed on the tail light assembly that's functioning differently? It sounds like the wires for those 2 sockets are in the wrong place in their harness. How comfortable are you with wiring and taking harnesses apart? Looks like a simple swap is in order. :yes:

The tail lights on the truck itself are functioning improperly, all the lights work just not when they are supposed to. I was just saying the only thing done to the vehicle is a pigtail which boggles me because there is a factory connection on it.
 

christo829

Member
Dec 7, 2011
497
Fairfax, Virginia
Do you have a picture of that pigtail? It sounds as if something was rewired incorrectly. If the
previous owner did a cut and splice, it's very possible they were trying something creative, and swapped
wires for some reason. If there's a factory connector, maybe one is wired correctly and the other is
not?

The rear lamp circuit boards aren't really constructed in a way where a failure would swap lamp
functions. If they went bad, parts of them would stop working, or work intermittently, but not trade
function. You might want to take one of them apart and see if there have been any modifications.

Check the manuals Mooseman has available. There may be wiring diagrams there that can help,
or someone else might be able to supply some.

It's also pretty improbable that both tail light assemblies (boards) would fail in the same fashion.

Good Luck!

Chris
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
I'm not real strong on electrical problems, but isn't that also a sign of a faulty ground?
 

christo829

Member
Dec 7, 2011
497
Fairfax, Virginia
Wooluf1952 said:
I'm not real strong on electrical problems, but isn't that also a sign of a faulty ground?

Faulty ground doesn't usually cause the circuits to swap function, just causes them to not function or function weakly. Besides,
there are separate grounds for drivers and passengers side tail lamp circuit boards, so both grounds would have to fail.

Not that it's impossible, mind you. I'm going by the observation that there's a pigtail that's been added to the circuit, so someone
worked on it after the fact, which makes it the most likely suspect for a failure or error point.

Cheers-

Chris
 

Greaser

Original poster
Member
Dec 30, 2012
4
Thanks a lot guys. I was afraid it was wiring. At least I'm good at it, I just hate going behind people and trying to figure out and correct what they did
 

Greaser

Original poster
Member
Dec 30, 2012
4
christo829 said:
Just in case you hadn't found them already:

http://gmtnation.com/f23/need-service-manuals-get-them-here-371/

There are wiring diagrams in there for exterior lamps, backup lamps, and grounds that will
help you trace what should be there vs what's been modified. I didn't specifically look for 2003,
but the wiring probably didn't alter much between 2002 and 2004, and both of those are included
in the documents.

Cheers-

Chris

Thanks a lot that will be a big help
 

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