Truck will start here and there NEED HELP

I have a 2006 Columbia with a series 60 14.0L Detroit, truck was doing fine until the other day the instrument cluster showed a drop in voltage tried to shut down and caught back up, I have tested power and grounds to ECM they are all good, I put a new ECM on replaced relays in the dash, the remaining problem is sometimes it will start and run or the instrument cluster says (no eng.) Or will show 0.0 on voltage but the truck turns over strong as over and I'm getting power

 

Replaced both main grounds to begin with because they were getting super hot when trying to crank, the ignition is do its job send power like it's suppose to

 

The truck turns over super strong even when the dash shows 0 volts I have checked everything I k ow to check and I can't make any progress, I can be standing by the truck and the problem magically fix itself or I can go home for the night come in the morning turn the key on and the instrument cluster show (no eng.)

 

finally figured it out! What had happen was someone had worked on this truck before and routed the ECM ground wire to the outside of the battery box to a remote place on the inside of the frame and the wires were making a poor contact thank you everyone for your help it has just been one of those boogers!