Could it be possible that since the engine isn't connected to the ground cable to the battery, that it could be trying to ground somewhere else, thus making the ECU through a check engine light?

 

Not sure about your wording... Are you saying that you have disconnected the ground or something? In any event, either the battery is properly grounded or it is not. It would not be making its own new path. There could be a new path if there is a short somewhere. But to start, maybe back up and start with what year car, mileage, what's been going on with it to bring you here. If you have the OBD1 set up, read the codes and post back. If you have OBD 2, go and get the codes read. Post them and then we can try to point you in a direction....

 

Very likely!

Nope!

 

+1

 

Does anybody have the location of where the ground cable is supposed to connect on the engine/transmission coming from the negative terminal? Thanks

 

It attaches to the tranny on the front about half way down.