[68z28kk]

The tank unit is the only ground to the gas gauge. With the key on and the tan wire in the trunk connector unplugged to the gauge. The gauge should read beyond full. If it doesn't move you need to test for 12 volts at the + side of the guage. If 12 volts is present and it doesn't go to full it's either the dash gauge or the resistor that is on the back of the gauge. All the other grounds under the dash don't affect the gas gauge operation. Once the dash gauge works as described above the tank unit is a resisted ground and is simple to test.