2002 Dodge Ram oil pressure gauge has gone out

I have a 2002 Dodge Ram 1500 with 117,000 mi., and recently my oil pressure dropped to zero. I immediately pulled over and shut it down. After towing the truck home I started it and everything was fine, oil pressure was good. Came to a stop and it dropped to zero again. No rattling or shacking of the truck. This time it stayed at zero. I changed the sending unit and nothing. I changed the oil pump and checked for engine sludge, still nothing. I hooked up a mechanical gauge and pressure is fine but still reads zero psi on the electrical gauge. Any thoughts, Thanks.