There are a ton of great minds in here. I am hoping someone has ran across my problem in the past and can provide some guidance.

I built a 383 and installed an SD TPI setup. I decided to start the engine on a Moates Ostrich with a customer bin file. The memcal was what came with the ECM and TPI set up that was purchased all together. Once I got everything installed and fired the engine up for the first time the engine ran VERY rich and wouldn't idle. The SES was on and a 51 code was pulled. This pointed me to the memcal being incorrect. Upon looking up the PN on the memcal I was using was from a 93 LT1. I had a new PROM custom made from a new memcal and installed it in the ECM.

Now the engine starts and does not run rich, but it still is not right. The SES is still on, but when I jump A and B terminals to pull the codes the SES light stays on and does not flash any codes. Using a digital volt meter and using the ground terminal of the ALDL I get 5 volts from the diagnostic terminal, just no flashing SES.

I didn't do anything but change out the PROM. There are no open circuits in the SES light and none in the diagnostic lead going to the ALDL. Everything that I have read says that if it is neither of the things mentioned aboved (open circuits) then the ECM is bad. Can the ECM be bad and still allow the engine to start up and run (albeit run bad)?

The only thing that I know I did from the time I pulled the first codes and now was mistakingly jump the A and M terminals instead of A and B. Could this have caused the troubles that I am having?

Thanks for any insight that can be provided!!

 

first thing to check is unplug the ECM & see if the check engine light is off when you turn the key back on. if the light is still on you have a short some where, if the light is off you may have a bad ECM. now would be a good time to check all your powers & grounds to the ECM. a test light would be better to check powers & grounds than your volt meter.
after you have unplugged the ECM & checked the light, if it was off, pull the MEMCAL & then put it back in and plug the ECM back in & recheck to see if you can pull codes.
it is possible you damaged the ECM, A is ground & M is the data line.
did you try to scan it?

 

Denn_Shah,

I did try to use TTS Datamaster with a MaStach adapter. The only thing I got when I tried to connect up was that the adapter was working, but no communication could be established with the ECM.

I'll try unplugging the ECM today. Also since writting my orginal post I read another post that talked about the SES blinking once briefly when you turn the key on. It does do this. That is when you turn the key on the SES blinks one time very briefly, but after that....nothing.

Thanks!

 

one more thing.....IF the ECM is bad, would it still start and run? I figured that if the ECM was indeed bad that it would not allow the engine to start.

 

in most cases the bad ecm won't effect your engine starting. Just make it run lean or rich and you car won't perform at its best. The ecm is looking for the right signals from your emission sensors and other parts hooked up to your engine. The your egine will still run if soem of these sensors go bad. Your ecm will compansate and just default. But if your ecm is really messed up like wrong prom chip installed maybe your car won't run i'm not sure. But I would try to find a ecm on TPIPARTS.COM or at least call them and see what they think.

 

The same thing kinda happend to me a while back on a L98 the problem was the fuse that controlled the FP and ECM was blowed it would start when it was cold but would not run off the sensors after it warmed up. I like to never chased it down because the ecm wouldnt let me pull any codes either check that out it might help ya somewhat.

 

its not unusual for the motor to start & run with a bad ECM.

i have worked on a good number of cars which would start & run fine with the only complaint being the check engine on. if i can't pull codes & i can't get data, i check the powers & grounds at the ECM, if everything checks good i order a reman ECM & go from there. the new ECM repairs around 90% of these problems with the rest having a short some where.

 

As Denn_Shah said it is most likely your ECM, I just had the same problem that you have, I just got the ECM today, cleared everything right up! The car ran, but not great had a stutter, hunting for an idle, couldnt pull codes, and would hardly shift (700r4). Under WOT it ran like crap. Anyhow unplug the ECM and check like Denn said, youll probably find its the ECM.

Also thanks again Denn_Shah on the alternator help quite some time ago, I havent forgot!!