03 Grand AM going through ICM every 20 minutes?

[TazMan]

Hi everyone. I'm really going nuts with this. Had my car sitting layed up for about 6 months. I just went to put it back on the road and the car ran good for 1 day and then the next day just died. No power to fuel pump. No spark. No code. Changed the 7x Crank sensor and the wiring harness to the ICM. No go. So I swapped out the ICM and coil packs for a known good one and it started right up. Great. I let it run about 20 minutes. Suddenly the engine starts misfiring, the rpm gauge started jumping all over the place like something weird electrical was happening, and it stalled. It won't start. Occasional spark for a minute trying to start but obviously severely out of time. Then right back to no spark, no fuel. I checked the wiring to the other sensors. The wires to the cam sensor had all melted and the coating was gone for them. For sure they had to be shorting. Got out my solding iron and my heat shrink. Fixed the wires all up. Connector was good. Changed the cam sensor while I was in there. Tried to start it, and nothing. No spark. No power going to fuel pump. I changed the ICM again to another known good one, and it started right up. So I let it run a while. Seemed good. Vacuumed down the A/C and charged it. So far it's running a good hal hour. Sat in it for another maybe another 10 minutes, and then all of a sudden the RPM gauge starts shooting up and down again, the engine starts misfiring, and it died. I tried to start it again. It misfired very bad, started, ran for a like 20 seconds, and died. Still, no Codes. I'm stumped. Does anyone have any idea?

[TazMan]

Ok, I had some more time to look at it today. It seems I'm losing ground to the ICM. I'm gonna head back out and try to trace it before it gets dark. Can anyone tell me where the ground for this comes from?

[TazMan]

Just got it figured out. It turned out to be some little module bolted to the transmission housing that was never tightened and kept losing ground. It seems to supply ground for the icm, computer, and not sure what else. I had a transmission put in by Amocco about a year and a half ago. Today I finally discover that they were nice enough to leave every bracket, bolt, and ground nut just hand tight. Transaxle brackets, ABS module, you name it and the bolt was just sitting in it hand tightened a bit. My first time in 15 yrs breaking down and going back to a mechanic and it cost me $2000 and a week of troubleshooting. Apparently $2000 only gets the car half assembled at these places.

[Purple pit]

Where was this module on the trans?

[TazMan]

Where was this module on the trans?

I called it a module but it's really just a ground junction. It's located on the tranny stud right behind the shift cable bracket where the cable connects to the trans linkage. You can't really see it unless you remove the bottom part of the air intake filter housing cause it's hidden under the exhaust manifold pipe that runs along the side of the engine there. It's a little black plastic square thing with a bunch of wires coming out of it, and on top of it there's a metal ring that mounts to the stud and provides ground for all those wires.

[Purple pit]

Thank you. I'll have to look at mine!

[TazMan]

Thank you. I'll have to look at mine!

No problem. If it helps, here's another one that was mounted up on top next to the air filter where I could easily get a picture of it.

[Purple pit]

That does help! I have to find it on my car(no time yet) and the GF's car(it's the one having problems).