* Faulty Fuel Level Sender: This is the most common culprit. Located in the fuel tank, it's a float-type sensor that measures the fuel level and sends a signal to the fuel gauge. A corroded, damaged, or malfunctioning sender will send inaccurate signals. This could be due to:
* Corrosion: Rust or build-up inside the tank can affect the sender's float or resistance.
* Float Problems: The float might be stuck, leaking, or damaged, preventing accurate level detection.
* Wiring Issues: Worn, frayed, or corroded wires between the sender and the instrument cluster can interfere with the signal.
* Bad Fuel Gauge: The gauge itself in the instrument cluster could be defective. While less common than a faulty sender, it's possible the gauge is failing internally.
* Problems with the Instrument Cluster: Issues within the instrument cluster's circuitry (beyond just the gauge itself) can misinterpret signals from the fuel level sender.
* Power/Ground Issues: Poor electrical connections or a faulty ground can lead to inaccurate readings. Check the power and ground wires to and from the fuel level sender and the instrument cluster.
* Computer Module (PCM) Issues (Less Likely): Though less frequent, a malfunctioning Powertrain Control Module (PCM) could, in rare instances, contribute to inaccurate fuel level readings, especially if it's also showing other erratic behavior.
Troubleshooting Steps:
1. Check the Fuel Gauge First: Does it move smoothly or jerk erratically? If it's completely dead, that points away from a sender issue.
2. Inspect the Fuel Level Sender: This often requires dropping the fuel tank, which is a significant job. However, you can try accessing the sender through the access panel (if your model has one) to visually inspect it for damage. Look for corrosion or anything obstructing the float's movement.
3. Check the Wiring: Visually inspect the wiring harness leading from the fuel tank to the instrument cluster. Look for broken, frayed, or corroded wires.
4. Test the Fuel Level Sender: This usually involves using a multimeter to measure the resistance across the sender's terminals. The resistance should change predictably as you manipulate the float. (Consult a repair manual for your vehicle for the correct resistance values.)
5. Test the Fuel Gauge: This is more difficult and might require specialized tools.
Recommendation: Unless you are experienced with automotive electrical systems and repair, this is a job best left to a qualified mechanic. Replacing the fuel level sender is often the most cost-effective solution, even if it's not the *exact* problem; if the sender is old, it's likely a source of future problems. Replacing the fuel pump assembly is another common repair since they are often linked.
