Thread: Harness and wiring information

If you pull the body harness that goes to the dash, the speedo should function with the grand prix cluster. The speed sensor is on the transmission.

The BCM itself and ABS are not functions of the PCM, so neither prevent the engine/transmission from working. You can't tune the ABS out because it's not a function of that controller and is not required.

You can't easily switch between dual zone and non dual zone controls, nor can you easily switch from the HVAC buttons itself if you are using the stock grand prix harness.

Originally Posted by wstefan20

Congrats on the fiero project! I'm working on one as well at the moment.

I'm a little confused what you're trying to accomplish exactly. Are you trying to completely integrate your gp harness with your fiero and have all functions work?

I'm thinking on replacing the entire Fiero harness with the GP harness, though it may be easier to buy a Firebird and use the harness from that to start ( then I can also have the dash to swap in)

I bought the Fiero with more electrical problems then I realized. it started and ran, but would blow fuses and act strangely ( headlights up and down, wiper speed erratic, radio blowing fuses, intermittent brake light function.. etc) which made me dig into the harness a bit where I discovered damage from rodents, poorly placed zip screws, and what i assume was an after-market stereo install that went wrong and was mishmashed back to the factory radio.

My original plan was to just 3800 swap and drive, but now that its winter i might as well fix everything I can.

you can buy this harness pre made for like 400 bucks. pencocks fiero forum has a guy over there who makes and sells them.

Originally Posted by Scottydoggs

you can buy this harness pre made for like 400 bucks. pencocks fiero forum has a guy over there who makes and sells them.

For me, there is damage to my factory harness in several locations- to use the adapter harness I'd first have to remove my harness and repair it. And honestly if I'm doing all the work of removing the harness, I'd rather spend the time fitting a harness that wouldn't require an adapter at all. I'm also not sure the guy Jscott is still around

Originally Posted by wstefan20

I've definitely been there! Good news is that the fiero body harness isn't all that complex.

The issue will be that in order to keep factory power windows and door locks (If you have them) and other things that can't be moved over since they're physically part of the vehicle will basically have to be reverse engineered to make sure it'll work and how to integrate it.

Would this be as easy as taking the connectors from the fiero harness, Removing the connectors from the new harness and then replacing them with the Fiero connectors? I've never dove this deep into the wiring of a car.

Originally Posted by wstefan20

The easiest route by far is to swap the complete dash from an f- body and use it's bcm and steering wheel column if possible. With this approach, you'd simply have to adapt fiero body features to this harness, then adapt the engine harness to it.

Of course, any small engineering things you get stuck on, I'd be willing to help here and there though!

I've got two potential fbody cars in the wings, one is a 3.8 the other isn't- any idea how difficult it would be to get teh 3.8sc engine harness to play nice with the non 3.8 harness?
I'm browsing some fbody forums and groups now, waiting for answers as well