Hey!! Gotta problem with a '97 Ram 5.2l.. died and won't restart, no spark, no fuel pressure. Checked all sensors for power and they all check good at 5v. Problem is the ecm is NOT sending a good ground to the sensors while engine is cranking but as soon as I stop the cranking the ground returns.. why won't the ecm send ground while cranking?

 

I'm not really sure what the ecm does with the ground signal from the various sensors. It's sends a voltage down one wire, gets a return from another..... which is what it uses to run the engine. Since you are getting no spark, and no fuel pressure, I would suspect one of the major sensors has failed. (cam, or crank position.) If the PCM doesn't see the engine turning it won't engage the fuel pump, or fire the coil.

 

I'm getting a ground signal from the ecm until I crank the starter but then I lose the ground till I let off the key. There are 11 sensors on the ecm sensor ground circuit and I've disconnected all of them but still have the same issue..

 

is the PCM getting data from the cam and crank sensors? Need to plug in, and see if it sees the engine is actually turning.

 

I had a similar issue with a Monte Carlo. I would test the battery and others connections and everything looked good.
As soon as I would use something or try to crank the car the ground dropped .
Ended up being a bad ground cable from the battery to the frame.
The shop replaced them (engine to frame and battery to frame).
problem solved. if you havent try testing the ground straps.

 

The pcm has two grounds going into it. Pin #A31 and A32(1996) not sure if it's the same in 97 but you may want to check that they have good body/battery ground.