diagram for 7 pin

[quikki]

I was wondering if any one had a diagram of the 7 pin receiver on truck.
I plugged in a trailer today but nothing worked the way it is supposed to.

 

[DavidC166]

Courtesy of a search.... here's an old thread....



RENORCR
Full Member
Towing Package trailer light hookup
? Reply #1 on: 01/16/04 12:53 AM ?

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I would check your owner's manual first under "Trailer Wiring Harness".
There's a diagram for the harness.

For a 03':
Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn Signal
Brown: Taillamps
White: Ground
Light Green: Back-up Lamps
Light Blue: CHMSL (Center High Mount Stop Light)
Red: Battery Feed
Dark Blue: Trailer Brake

 

[ShapeShifter]

I was wondering if any one had a diagram of the 7 pin receiver on truck.

This is the plug on the truck's wiring harness that plugs into the back of the trailer socket under the bumper.

​

While this is out of the 2002 shop manual, these plugs should be standardized, and both the wire colors and relative pin positions should be the same for all years.

Keeping in mind that this is the plug on the backside of the connector, the rotated orientation, and the shape of the pins on the front side of the connector might be somewhat different, but the relative order of the pins should be the same.

I plugged in a trailer today but nothing worked the way it is supposed to.

Can you define the problem a little more clearly? What happened, and what did you expect to happen?

If you are having problems with lights working, you might have a bad or corroded connection, a burned out bulb, or a blown fuse. (The Av uses independant fuses for the trailer circuits, so that a trailer fuse might be blown preventing the trailer lights from working, even though the lights on the Av are still working.)

If you are not getting battery feed voltage or trailer brake power, you might need to install either the Stud 1 or Stud 2 fuses under the hood. Even if it looks like there is a fuse there, check it carefully: some trucks shipped with a dummy fuse installed that looks like a regular fuse, but it is not.

If you are having problems with your electric brakes, and you are using a cable plugged into the connector block by the driver's feet, make sure you have the right cable for your year truck. While the connectors will physically mate, they moved some wires around between 2002 and 2003. If you try to use a cable meant for a different year truck, you will have problems. I think one of the symptoms of using a 2002 trailer brake controller harness on a 2003 or later is that the brakes may set when you turn on the headlights, and a fuse may blow if you step on the brakes. (Or something else equally drastic.)

There are lots of things that can go wrong, the least likely is that the pin definitions on the connector are mixed up. Give us more detail and we might just solve the problem.

-- SS

 

[quikki]

Everything was mixed up

If we turn right signal on the left would flash,
but if It stepped on the brake it would flash right
no clearance light either

 

[ShapeShifter]

Everything was mixed up

Wow, that is wierd.

That plug should be wired according to an industry standard, and I would be really surprised if the truck wiring was scrambled. What is the trailer wiring like? Was it wired from the factory that way, or was the 7 pin plug wired later? Are you using some sort of adapter?

Can you plug the trailer into another truck (or another trailer into your truck) to help isolate the problem and determine if it is in the truck or the trailer?

-- SS

 

[RENORCR]

If I remember correctly, you had to use a dealer specific wiring harness.
You couldn't just go out and buy one of the shelf.
Anyone remember that topic?

 

[ShapeShifter]

If I remember correctly, you had to use a dealer specific wiring harness.
You couldn't just go out and buy one of the shelf.
Anyone remember that topic?

If you're talking about the harness that goes between the socket by the driver's feet and an electric brake controller, I belive you are right. (Although supposedly some of the higher end controllers are available pre-wired with the right vehicle-specific connector.)

But if you mean the socket on the back of the bumper where the trailer plugs in, that should be an industry standard and no special wiring should be required.

-- SS

 

[Lockout]

GM did change the harness for the 2003 and up model years. It sounds like you were using a 2002 connector on a 2003 truck. You will need to go to the dealer and get the correct harness.

 

[ShapeShifter]

A couple people are talking about a "changed harness." Are you referring to the electric brake controller haness that is used inside the cab, or are you talking about somethng outside the truck that is used at the plug on the back bumper?

If you are talking about the inside brake controller harness, it is definitely a problem using one from the wrong year, but my understanding is that it does not cause the type of problem that is being described. For example, quikki is talking about left/right turn signals being scrambled: the brake controller harness has nothing to do with turn signals. Using the wrong brake controller haness causes things like the brakes to set hard when the headlights are turned on.

If you are talking about something outside the truck that connects to the plug by the bumper, that is news to me, as I've never neard of such a thing (other than the 7 pin to 4 pin adapter, which is not model nor year specific.) If they changed the wiring and meaning of the pins on the back bumper, that would be a really bad thing as the definitions of those pins are an industry standard. It would be sheer stupidity to mess around with that!

When talking about "harnesses" can we please be a bit more specific?

-- SS

 

[RENORCR]

I went and checked the 2003 manual. Based on the 2003 diagram. Pin location are the same, except for a wire color change. The Ground wire was change from White (2002) to Black (2003).