Most likely cause is an open circuit between the dash and the sending unit in the tank. Unlike all other manufacturers that read empty when there's a break in the circuit, GMs read full. If you can find the sending unit wire at the tank, unplug it and ground it to the body with a jumper wire. If the dash gauge reads "empty", the sending unit is defective. If the gauge stays on "full", there's a break in that wire or a loose pin on the gauge cluster.
Friday, February 17th, 2012 AT 10:36 PM