The check engine light is on, so I take my car to the shop (The car runs great BTW). They tell me I need a new ECM which will run me about $300. I need some input to be sure this is legit. I'm confused because the car runs fine and smooth. It does have an "upgraded" cam in it, but no other mods aside from an MSD optispark distributor and chambered cat-back exhaust. Do I really need a new ECM, or does it simply need to be reprogrammed? It all sounds kinda strange to me.

 

This site will famaliarize you with pulling codes.
http://www.corvettephotographs.com/c4vettes/index.htm

It's not that difficult so give it a shot.

 

There's a lot of good info on that site, thanks for posting it.

 

Only GM cars 98 and above can be reprogrammed. All others have to have the PROM replaced. What year is your car? I am curious as to why the ECM has to be replaced just because the CE light is on? What codes did they pull?

 

Not sure on the codes. I'll ask for them when I pick it up today. If they don't/can't tell me, I'll try this website mentioned above. My car is a 92. If I have to get it replaced, I figure why not have PCMforless do it instead. It would be cheaper ($199 vs. $300). Then again, I have no clue if the PCM and the ECM are the same or different. It sounds like they are different. I'll know more after I've pulled the codes.

Thanks for your comments fellas.

EDIT: I've reviewed the website above, the PCM and ECM are essentially the same thing....

 

Early days, the cars had ECM (Engine Control Module), and it just controlled engine. PCM (Powertrain Control Module) controls engine, transmission, and anything considered powetrain. Be careful getting cheap modules, because they use cheap components to reman them. A/C Delco makes remanned computers for a reasonable price. Just make sure to swap your prom and CALPAC out of your old ECM.

 

The code pulled was 26, which according to the website above does include possible ECM failure. The strangest thing is the performance of the car. It runs great, better than it ever has. All those problems with missing in the upper RPMs are gone. It pulls all the way up to 6k rpm. The torque is also noticeable down lown. One of the best parts is the gas mileage appears to have improved as well (when I'm not screaming my way to 6k).

I attribute the improvements to the MSD vented optispark distributor, new plugs and wires, and new water pump. I also brought the car to the emissions testers and it passed. So, aside from the check engine light on, the car is a rocket with no noticeable issues. I might wait on replacing the ECM for the moment.

 

I own a 92 vette and have had the same problems I got mine all corrected
by the way you pcm can be recalibrated and remanned. I would sugest that you contact the AC delco rep at you local dealer to get the address Your pcm is matched to the vehicle you own so just getting a new onw won't correct your problems i had mine updated and got a lifetimewarenty with it. any questions feel free to asI have found that the 1992 corvette is an animal all its own nothing ususaly fits from another vette

 

Frank, what if the cam I have is aftermarket? Worse yet, what if I don't know the cam specs? I can only assume they would need to know this to have the ECM programmed properly. Also, someone else said only 98+ GM cars can be reprogrammed. Did you mean they replaced it or was it actually reprogrammed? I'm going to ask the dealer about it regardless.

P.S. When I bought the car from the dealer 3 years ago they didn't know the cam specs and they tell me the previous owner doesn't know either. Go figure on that one.

 

The prom can be reprogrammed but most dealers will not do it. a good mechanic with a tech 2 or higher computer can accomplish it.As far as the cam profile the pcm ecm will compensate on a demand basis for any advance timing or fuel demand that is why i said do not replace you present unit have it rebuilt
the pcm/ecm has 5 different sections in it that controls the electrical impulses and timing and fuel demand. If you do replace it make sure that the pcm/ecm has the identical part number stock numbers. It is easier to replace the e prom and probably less expensive e bay has many different choices and usually are not very expensive. you just have to shop around. But i have had a lot of experience with my 92 thats just some of the things that the pcm/ecm will do. Don't get discouraged you hae to experiment. do you have any engine pcm/ecm codes now.