Could be bad gauge or float stuck in fuel tank
you will have to drop the fuel tank and remove the pump gauge unit. it maybe stuck, broken wire, or simply bad.
check sending unit in tank and check gauge for proper operation and connections, and grounds
how do you fix a gas guage on a 1989 ford aerostar
Then fix it
Float in tank is stuck or defective gauge Sounds like the sending unit is stuck in the full position.
Have you checked the gas floater in the gas tank?
Where is it stuck? on full or empty? if on full you got a bad ground, if empty you got a bad float.
Sounds like a bad gauge sensor or a bad tank sensor (or both).
check for broken wire from fuel sender unit in fuel tank to gauge. check fuel sender unit for proper operation. float may be stuck in the tank then check fuel gauge
You should gas mileage will suffer otherwise
The most common cause for a 2002 Toyota Highlander's gas gauge to be stuck at three quarters of a tank is a faulty sending unit. The sending unit is designed to detect the current fuel level and relay it directly to the gauge.