Alright folks, here'* the deal. A buddy of mine is going to sell me a Bonneville with a very beat up body and wheels for $300, but it has a 3800 Series II. I own a '91 Grand Am, and I would love to swap the 3800 Series II into my car. I'm mainly confused about how to make the gauges communicate with the Bonneville computer, and what to do about the wiring harness. Please respond, and thanks for the help!

...good luck. That'* a nightmare and a half.

OB2 trying to communicate with ODB1... yuck.

you would have to get a oem service manual, so you can put what needs to be put back what needs to be there modules wise. depending on the year there theft module and fuel enable stuff to worry about. and the emissions stuff. you can have this stuff turned off. but you would still need alot of the wiring and possibly the gauge from the newer one, they talk to the pcm via a serial bus, like a computer.

there is a much easier option, you can get a 3400 replacement block, depending what came in your car it may be as easy as putting the stuff from your car on it and finding someone to tune your chip. the 3400 has about the same as the 3800

Yea, this is a nightmare just in wiring itself. Your taking an OBD2 engine and attempting to convert it to OBD1. The PCM is going to bitch and whine about being in an OBD1 environment and cause so many issues, that you would wish that you hadn't done it.

not to mention its only what 200hp, there are much easier ways to get that

What year is the Bonneville? How important are stock Grand Am gauges to you? Because if you say not very, then this gets a lot easier from the sounds of it.

If it'* a Series 2 engine, then it has to be at LEAST a 95 or newer. Even with a 95, this is completely a different breed of PCM vs a 91 chassis. And no, it'* not going to get easier regardless of year. It will actually get HARDER or next to impossible the later the PCM is.

Or in english.... a Series 2 is not plug-n-play in a 94 or older chassis.

That'* what I was afraid of. Thanks, everyone! I'll probably just repair everything I can on the Bonneville and keep both or sell the Grand Am.

I'm not sure how the whole OBDI/OBDII thing works, but would using a fully programmable ECU like a MegaSquirt make it possible?

those are not cheap. it would be cheaper to use the gm pcm for the bonnie and have it tuned or get HPT. hpt is like 600, and you can turn off the fuel enable for the security, and any emissions you dont want to bother with. Or you can have it done for a few hundred but you get it tuned one time, not real handy for something that custom. then what ever it costs for a gm service manual for the car.