What part is bad if a full tank of gas registers as only half a tank. Is it the gauge or does it have a fuel level sensor.
It could be both or a resistance in the sender wiring, you will have to check it out, if you unplug the fuel tank sender the gauge should swing way past full, if it does then the gauge and wiring checks good and the sender is faulty, if it don't then you will have to pull the instrument cluster out and check resistance on the wire from the cluster connection to the sender if that check good then replace the gauge. HTH
The sender in the fuel tank may not have a good ground that is why the fuel gauge is inaccurate.
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