Here's a breakdown of why this is the most probable cause, and other less likely possibilities:
* Fuel Level Sending Unit (most likely): These units are prone to failure over time, often due to corrosion, debris in the tank, or simply wear and tear. A stuck float or a broken potentiometer within the unit will prevent it from accurately reporting the fuel level.
* Gauge Cluster (less likely): While possible, it's less probable than a faulty sending unit. A problem with the gauge itself is usually indicated by erratic readings or complete failure, not consistently high readings.
* Wiring (less likely): A short or break in the wiring between the sending unit and the gauge could cause inaccurate readings. However, a short usually leads to erratic behavior or no reading at all, not a consistently high reading.
* Ground Issue (less likely): A poor ground connection in the fuel level circuit could potentially affect the gauge's reading, but it's less likely to cause a consistently high reading.
In short: Start by suspecting the fuel level sending unit. Replacing it is usually the most cost-effective solution, and if it's truly malfunctioning it is the repair that will fix the problem. You'll likely need to drop the fuel tank to access and replace the unit – a job often best left to a mechanic unless you're comfortable working with fuel systems. Before doing so, you could try disconnecting and reconnecting the fuel level sending unit electrical connector, but that rarely produces a lasting repair.
