1. Simple Checks (Do these FIRST):
* Empty Tank?: Sounds obvious, but sometimes the gauge just sits on empty. Try filling the tank. If the gauge doesn't move, it's likely not just low fuel.
* Loose Connection: Check the connections at both ends of the fuel level sending unit wire. The sending unit is located in the fuel tank. This is the most common cause. Corrosion is a frequent problem.
* Blown Fuse: Check your owner's manual to locate the fuse for the fuel gauge. Replace it if blown.
2. More Involved Issues:
* Fuel Level Sending Unit: This is the most likely culprit if the simple checks fail. The sending unit is a float inside the fuel tank that moves with the fuel level and sends a signal to the gauge. It could be faulty, corroded, or stuck. This often requires dropping the fuel tank to replace.
* Fuel Gauge Cluster (Instrument Cluster): The gauge itself could be malfunctioning. This is less likely than a sending unit problem, but possible. Replacing the cluster is usually more expensive.
* Wiring Issues: A break or short in the wiring between the sending unit and the gauge cluster could interrupt the signal. This is difficult to diagnose without a wiring diagram and a multimeter.
* Ground Issues: A poor ground connection can affect the gauge's readings. Check for corrosion on ground wires related to the fuel system.
3. Less Likely but Possible:
* Computer Module Problem (PCM): While less common, a problem with the Powertrain Control Module (PCM) *could* theoretically affect the fuel gauge, though it's usually associated with other issues as well.
Troubleshooting Steps:
1. Start with the simple checks: Fuse, connections, and ensuring the tank isn't actually empty.
2. If those fail, suspect the sending unit: This is the most probable culprit.
3. Use a multimeter: If you have some electrical knowledge, you can check the voltage at the sending unit connector with the ignition on to see if you're getting a reading that changes as you move the float (if you can access the float somehow). This will help determine if the problem is the sending unit or the wiring.
4. Professional Diagnosis: If you're not comfortable working on your car's electrical system, take it to a mechanic. They have the tools and expertise to properly diagnose the problem.
Remember safety first when working with fuel systems. Always disconnect the battery negative terminal before working near the fuel tank. Gasoline is highly flammable.
