1994 Rear Wiring Harness
 

I am completely re wiring my 94 Sierra with a painless wiring harness. I removed all computer controlled components etc…

The loom under the Hood with the Taillight wires has an extra yellow wire (2 yellow wires instead of one) that goes all the way to the Taillight harness. It also has a purple wire - that does not make it back to the Taillight harness. I can’t find these in the manual. They don’t appear to be aftermarket, they are in the Factory Loom.

1994 C1500 Sierra GT Single Cab Short Bed
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Re: 1994 Rear Wiring Harness
 

I am taking a guess, but maybe for trailer wiring or trailer controller

Re: 1994 Rear Wiring Harness
 

That was my initial thought for the purple wire since I can’t find it in the manual. The Yellow controls the left turn signal per the manual. So I don’t know why I would have 2 Yellows. It’s also odd that they are in the factory loom. It’s like it came that way from the Factory.

I was wondering if there were any Trailer Packages from the Factory? With it being a GT and a 1500, I wouldn’t think it would have been on the list for a special tow package from the Factory.
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Re: 1994 Rear Wiring Harness
 

The extra yellow wire is to hook up a third brake light for a cap. It is terminated with a blunt splice near the rear of the truck. You can remove it if you'd like. I'm unable to find the purple wire in my diagrams

Thanks for the info on the yellow. The Purple wire still has me stumped. The rear harness was a bit of a spliced mess, so I couldn’t see and factory termination, just a bare wire hanging on the yellow. Usually people don’t go to the trouble of adding to the factory loom, so I am really confused about the purple wire.
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