i've noticed that most of the aftermarket wiring harnesses for swapping an ls1 in something requirre the use of a 99 up f body computer. whats wrong with the 97-98 pcm? i found a deal on all the fuel injection stuff off of a 98 ls1 t/a and dont want to buy it if its not gonna be worth a damn. any help is appeciated.

 

The main thing is it is harder to tune. If you have an option on what year computer to buy, 99+.

 

The only difficulty I'm familiar with is that the idle settings are not as precise as the 99 and up.

 

My understanding is less resolution in the tables and maybe less tables. Still learning here as well though.

 

You can run a 99-up harness and PCM on the 98.

Jon
PSI

 

My 1998 C5 still has the stock PCM and it was quite easy to tune. The best part is that 97-98 cars don't require a license to tune for EFI-Live (saves you $100).

The 1998 PCM doesn't support custom operating systems (for those who want speed density tunes, dual tunes, etc). So for advanced users or wild mods the 1998 PCM is not the best choice.

 

Less memory, slower processor. The 1998 PCM -DOES- support custom OSes with HP Tuners, I have a 2 BAR 1998 PCM in my turbo car.

You have to repin the 1999+ harness to run a 1998 ECU, several pins are relocated.

 

I am running a 98 pcm/harness in one of my rods. I had to change a couple of wires to run the later model coils/center bolt valve covers engine. Speed density tune runs like a top.

 

Pretty much already covered. 98 is fine. Pro tuners mainly don't like 'em due to the extra work it takes to tune w/ them & the interpolation required in some cases. I have been using one for several years & run an OL, MAF tune (open loop, MAF) without issue.

 

Apologies for the 'jack. Years back (before I had a clue) I bought a '97 C5 engine harness off E-Bay for a future project that didn't pan out. Can it be used for anything? I don't mind repinning connectors, but can it be used with a newer PCM?

 

Re-pin PCM, ECT switch (AKA sensor) is a 3 wire on a pre-99, so harness gets moded for 2 wire ECT switch. May need to modify harness if a MAF w/ integral IAT sensor is used. Pre-99 MAF uses IAT sensor separate from MAF. That's all I can think of related engine harness.

 

Yeah that's the big draw back is tuning with one. If you know what you are doing there's nothing wrong with them. I've built 800rwhp 98 Trans Ams with twin turbo's and had no issues at all. And just last year I did a 94 formula LS1 conversion with one and it worked out great.

 

Sorry for off topic.


Rick Speed,

Cleveland? Maybe I know you??? Even if not, you may want to hang w/us. We have cruises from time to time. Probably should continue this through PM's. So, if you want to discuss, send me a PM.

 

how to repine the 99 ecu to a 98 horness

 

Good question. It's been 10 years since the last post here....

 

https://www.mrk-motorsports.com/wp-c...o-1999-PCM.pdf try this link, I think it pretty much covers it