Needs some help with finding the ECM brain....

**Stephanieingulfshores** · 12-05-2016

Bear with me folks, I am a newbie and a chick....need I say more? We have 2 Grand Prix vehicles. One is a 1997 that runs like a scalded dog but the bells and whistles as well as cosmetically well, she has seen her better day. The other car is a 2002 in absolute fine working order all except for the ECM brain. A mechanic told us that it just wasn't communicating and could just need to be cleaned or replaced. My 2 part question is this...where is the ECM brain located on both models? We would like to clean the one on the 2002 to see if that worked. If not, we were going to see if we could put the ECM from the 1997 in the 2002 and then just send her to her final junkyard destination. Wouldn't that be possible if the two part models are interchangeable? We just need to know where to find them. I appreciate any and all help and suggestions. Have a wonderful day!!!

Stephanie

**Bronco Boy** · 12-05-2016

Originally Posted by Stephanieingulfshores

...where is the ECM brain located on both models?

Left front corner, inside the air box.

.....put the ECM from the 1997 in the 2002 and then just send her to her final junkyard destination. Wouldn't that be possible if the two part models are interchangeable?

Won't be interchangeable due to the years difference.

**Fivefingerdeathpunch** · 12-05-2016

The 1997 computer is a year only item. You won't be able to plop it in the 2002 model year car and drive away.

**Stephanieingulfshores** · 12-05-2016

Thank you!

**Stephanieingulfshores** · 12-05-2016

So here is my follow up then. The issue with the car is that while driving (after making a few stops) the car will start to sputter and not want to shift gears. If you pull over and turn it off, give it a minute and then restart it will continue driving fine usually until you have made many stops again. The mechanic said the brain just wasn't responding. Do you believe if we took it out and cleaned it that the problem could be corrected? Also, if we found another ECM from a 2002 grand prix, can they be interchanged? Would the new ECM have to be programmed at a dealership?

**Fivefingerdeathpunch** · 12-05-2016

It seems unlikely that the computer would have some sort of weird processor fault or driver problem after the short drives like you are saying. I wouldn't think anything is overheating inside of it and causing issues.

This is where taking time with a live data scanner would be wanted, watching all parameters and see where some sort of problem may come from. Someone could also be checking fuel pressure, transmission controls and so on. So to say that just the computer isn't responding anymore seems like a complete guess at the problem to me.

If you found another computer from the same year with the same engine/transmission combo you could just put it straight into the car. It may toss the sercurity light on but that can be solved with doing a security re-learn and it should allow the vehicle to run just fine.

Pretty much any computer from a grand prix that is from 99-02 would drop right in. 1997 being year only and 98 technically is different too because they changed the throttle body design in 1999 and thus the calibration is slightly different.

**Stephanieingulfshores** · 12-05-2016

[QUOTE=Fivefingerdeathpunch;1455368]

This is where taking time with a live data scanner would be wanted, watching all parameters and see where some sort of problem may come from. Someone could also be checking fuel pressure, transmission controls and so on. So to say that just the computer isn't responding anymore seems like a complete guess at the problem to me.

The mechanic did that. He hooked his computer up to it and said it wouldn't get a read at all. That is when he said it would be the ECM and may need to be cleaned or replaced. Just our luck!

**Fivefingerdeathpunch** · 12-05-2016

If he couldn't get the scanner to read the computer then there is a problem with the wiring to the obd 2 port.

Double check your CIG lighter fuse, if that is blown the scanner will never talk with the computer.

**Scottydoggs** · 12-05-2016

sounds like the fuse blew for the obd2 port, check the fuse for the power port. or see if it works, if its not working then the fuse blew. im guessing the check engine light is on? and he cant scan the car for codes?

**Stephanieingulfshores** · 12-05-2016

Originally Posted by Fivefingerdeathpunch

If he couldn't get the scanner to read the computer then there is a problem with the wiring to the obd 2 port.

Double check your CIG lighter fuse, if that is blown the scanner will never talk with the computer.

I will check that out next. Thanks!

**BillBoost37** · 12-05-2016

Problem 1 is the mechanic is aiming high with that guess, and 99% he is wrong as others mentioned.

When it starts to act up, lift the hood with it running the tap your finger (thump thump thump) on the MAF sensor. Scotty will post a picture of it in a second. Be patient, he's getting old.

**Stephanieingulfshores** · 12-05-2016

Originally Posted by Scottydoggs

sounds like the fuse blew for the obd2 port, check the fuse for the power port. or see if it works, if its not working then the fuse blew. im guessing the check engine light is on? and he cant scan the car for codes?

Well, the cig lighter works fine as does the port on the side of the console. We have a handheld OBD scanner and I plugged it in and it instantly says "no codes". When I plug it into our Jeep it goes through the scanning process first. Does this sound like there is an issue with the OBD port still. If there is a problem with that port could the cig lighter and power port still work fine? Oh, and no, there is no check engine light on at all. That is what is weird!

**BillBoost37** · 12-05-2016

Could just be the differences in the Jeep vs GP.

I feel good about the maf or a crank sensor.

**Scottydoggs** · 12-05-2016

why not just tell her its the square thingy on the top of the throttle body with a plug to it? i got no pics of a maf. tap it if the idle gets funky, or clears up, the maf is likely bad.

you can also engine off, unplug the maf, then fire it up, if it runs better the maf could also be bad, or if you see bare wire or crackes in the wire insulation the wires could be bad to the mafs plug.

**BillBoost37** · 12-05-2016

Thought you had the picture. Specially since you were single handedly the reason why photobucket disowned me from you linking all the time

**Stephanieingulfshores** · 12-05-2016

I guess I should have prefaced this whole thread by stating that about 4 years ago the car was having an extreme hard shift problem, we took it to the transmission guy and he had to put a whole new one in. Lots of money later we got it back and it ran fine for about 6 months to a year. That is when this problem started. We took it back to him and he said it was not the transmission at all. As of now, when you start it up it has a high idle for a few seconds and then calms down. Starts out fine and then if you make a few stops it will start lunging when shifting. Hard to explain really. But like I said when you turn it off and let it rest for a few minutes it will usually work fine for a while again until making stops. I googled a picture of the MAF so we will try tapping it next time it acts up and see if that is the case. I hope you are right because that sounds a whole lot easier than replacing an ECM. You guys are the best!!!

**Scottydoggs** · 12-05-2016

how about the check engine light? it on?

**Stephanieingulfshores** · 12-05-2016

Originally Posted by Scottydoggs

how about the check engine light? it on?

Nope, not at all.

**Mitch R** · 12-05-2016

Yup, it's unlikely to be the pcm. Unplug the maf sensor and see what happens. Its the black box on top of the throttle body, has a three pin plug. Also check for obvious wire failure as I had that happen on my 98 GP. When you first start it, it will run rough, maybe even die and your SES light should come on. But after about 15 seconds it will realize the maf is unplugged and will run using the map sensor instead. If your problem goes away then that's your problem

**Scottydoggs** · 12-05-2016

could be the maf then, they can sometimes act up like this and not set a code. do not get a aftermarket maf, they cost like 160 and dont work well at all. best to find a junk yard maf, or used off ebay, they run about 40 used for a oem one.

on top the maf is numbers, thats the part number for your maf, search that and you'll find it pretty fast. maf stands for mass air flow.

make sure the power port is working, and then you can get it scanned for codes after it acts up, but dont turn the key off, scan it running, there maybe a pending code. turn the key off and the code goes away. so dont turn it off.

autozone and most parts stores will scan it for free.