[PeteA216]

From the battery, theres one thick one going to a belt accessory bracket most likely cradling the altenator, and another, thinner one also directly from the battery bolted directly to the quarter panel. On the back of the motor, there should be a bare copper grounding strip coming from the engine head to somewhere along the fire wall, sometimes sharing a ground with the heater core. Get a Hanes manual for your car, and that will show you all the wiring schematics, and they can be fairly easy to read. This will help you locate the main ECM ground, which could too be at fault simply due to the fact that the ECM controls basically all engine functions.

Also, have you checked to see if you have any engine codes?