Wiring a trailer harness on a 2008 Grand Prix

I just installed a receiver hitch on my 2008 Grand Prix and need to wire up the harness. Does anyone know off hand which color wires are for the turn signals and the lights? It would save me a bit of time. Thanks.

You might want to think twice about trying to tow with that car. It’s mechnical twin (the Impala) is rated at maximum weight of 1000 pounds, with only 100 pounds max on the tongue. There’s a reason there’s no factory trailer towing package for this vehicle. You also may run into warranty snafus should you try to make a claim.

Thanks for the tip, and oddly this car is replacing my 2003 Impala that I also used to pull my small trailer with light loads. I’m not looking to pull anything heavy, or for anything more than just a few miles. Most of the time I use the receiver hitch for hauling my bicycle. Anything heavy I have delivered. I should have checked out the wiring before I trading in the car, but I didn’t get a chance, and they probably would have changed the wire colors too.

Most newer vehicles come equipped with connectors in the factory wiring harness to make installing trailer wiring just a plug in and go operation. However, when I checked 3 manufacturers they did not show a plug-in harness for your car.
Either they just don’t sell one or one isn’t made.

I’m wondering if they didn’t put factory triler wiring harness plugs in your Pontiac for the reason given by FoDaddy, not practical.

This idea would be tough to do on a newer model like yours (I don’t know how many years are similar body) but I found a wrecked car at a take-it-off-yourself recycling yard.

I cut the taillight harnesses with connectors on both sides, taking some wire pigtails with them. When I got home I made plug-in jumpers for both sides of my car and ran trailer wires from them. Using a test light it was easy to identify.

I had operating trailer lights and could simply unplug them to return the car to factory stock (in case of warranty issues or other problems). I hate cutting into a stock harness!

On a GM, I believe brown is the tail lights, yellow and green are the signal/brake lights and white or black is the ground.

It should be pretty easy to figure out, you probably will just need 4 wires:

left turn/brake, right turn/brake, running lights, ground.

Have someone sit in the car with it running while you look at the rear lights. Have them press the brake and note what lights come on, then -while still holding the brake- have them turn on one of the turn signals. If the brake light on that side begins to flash (i.e. the brake light bulb is flashing) then you are good to go. Use a test light or multimeter to find what wires are being powered when the brake / signal is powered. Use that test light to find what is powered when the parking lights are turned on, as well (license plate lights are a good bet here).

After that, go to your favorite autoparts store and buy a spool of 18 gauge wire, wire “taps”, and a 4 pin trailer harness. Tap the wires and run them one at a time down to the 4 way harness connector at the hitch.

Use this diagram to get the wire order correct on the plug:

Tape it all together as a neat harness and tuck everything in (use zip ties!) so that it won’t drop under the car and get snagged by road debris or drag on the ground.

And that’s all there is!

Go to a parts store and see if there is a plug in adaptor for your car. There are many adaptors that can just tee into a wire harness connecter.

With the advent of separate brake lights and turn signal lights it isn’t as easy to wire in your own connecter anymore. Many times you need a convertor to adapt this system to your trailer connecter.

Be careful. Some vehicles have a board that control lights. That board has the “flasher”, relays and other stuff. The components might not take higher current. Tapping into the wiring of these vehicles could be an expensive mistake. They require an isolator with relays for the trailer lights to get their power directly from a battery feed.

As I stated previously, I checked several trailer wiring manufacturers. They all showed no plug-in wiring available.

Thanks. You are right about the yellow, green and brown. I was able to get it wired up in just about 1/2 an hour.

Thanks to everyone else that replied also. Your help was appreciated.

KnucklesU Got It Working!

Thanks for the “thanks” to all of us.

I’m glad Bing got you going.

We don’t always get feedback after our attempts to help.