So I've got an issue with my '00 Grand Cherokee. When I start the car (or try to) it runs incredibly rough. Sounds to me like a timing related misfire, to the point where it's not even driveable.

What I do know:
Fuel pump is running, no reason to believe pressure isn't there.
I can't connect to the ECM with my code reader- SES light on
My tachometer still works.
Voltmeter does not work, which stopped when this issue arose- not sure what to make of that.
Other small odd things have happened with instrument cluster- odo display lights acting up, etc.

I need to double check all my spark plugs/cables, but I think they're okay. From what I gathered elsewhere it looks like a crank position sensor, but unless the tach reads from cam speed, that doesn't line up. Could it be the ECM failing?

Does anybody have experience with the CPS on these, is it hard to get done? I'm hoping it's a simple ignition issue but doubt it. Really don't want it to be ECM related

 

Hi I only have experience with ZJ 4.0 but I would say that you should also check the distributor and the rotor, they can be burnt and have bad contact, what can cause ignition failure.
And welcome on the forum.

 

It sounds to me you've got an electrical issue in the dash or wiring hardness. Check the connectors to the PCM for being loose or corroded and all your grounds. The CPS wouldn't cause the dash guages to not function.

Worst case, get your dealer to do an electrical diagnosis. I'll cost you around $100 but you'll know what's wrong after that. Don't go shot-gunning parts at it hoping to hit the right one! What engine do you have? is it the 4.0 or the 4.7 V8?

BTW, Welcome to CF!