Hey fellas. Ive got a 1999 sunfire gt.. its got sunroof and power windows. 2.4 5 speed. The computer come out and got ran over yatta yatta yatta. So, I think I can splice the harness back together and salvage it, and use a new computer. Do I NEED a 99 comouter? Also, if I do end up changing the harness how big of a job is it? Like I said tue harness isnt to bad but if it comes to it and I cant get it runnin with that harness ill swap it. Any help appriciated, thanks fellas

Yes, you'll need a 99 computer as the 98 had EGR and the 2000+ uses Class 2 instead of UART for communications with the rest of the car. 99 is a unique year for the 2.4L PCM.. well, the programming at least. You could use a different PCM and just have GM flash the program you need into it, but that's a bit of work.

The harness that goes to the PCM is part of the engine harness... which connects to all the engine bay components and the fuse panel, then mates to the rest of the car at the firewall under the airbox (known as connector C100). You should be able to use a 99-02 as long as it's for a 2.4L with 5 speed... if it's an automatic, you'll have to modify some wiring.

okay, thanks. does anyone have a diagram for the computer? the wiring?

Junk yard bro may b a cavalier one would work

Well you need a 99-02 LD9 computer, but need a 99 flash on it.

Since the pin outs and protocols are different.


Lenko is 100% correct.

I would get a 99 5-speed engine harness if it was me. Either sunfire or cavalier.





PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO