Dave,
Follow the wiring back into the cab if you can, and then disconnect from any internal parts or circuits, and then check sender and wiring together from under the truck ..... that will...
Dave,
Follow the wiring back into the cab if you can, and then disconnect from any internal parts or circuits, and then check sender and wiring together from under the truck ..... that will...
Sounds like a short cct to earth on the wire to the main tank gauge or a faulty main tank gauge.
Is it reading full or off scale high?
A fault like that will cause the sub-tank computer to fault...