P25D9: Fuel Level Sensor C Circuit Low

What it means

The Fuel Level Sensor C circuit signal is below the expected threshold. This identifies a low circuit condition but does not prove the sender is shorted.

At a glance

• Usually lights the check-engine light

How it works

Fuel Level Sensor C sends an electrical signal that the vehicle uses to estimate fuel level. P25D9 means that signal is below its expected threshold; this describes the circuit condition but does not prove the sender itself is shorted.

Common causes

Most likely first.

1. Internal short in the sender resistor
2. Signal wire shorted to ground
3. Connector pins corroded - high contact resistance

Symptoms

• Fuel gauge may read inaccurately or at an extreme
• Fuel level warning may appear at the wrong time

How to diagnose it

1. Save freeze-frame data and compare the Fuel Level Sensor C scan reading with the gauge and known fuel level.
2. Inspect the tank-module connector and accessible wiring for corrosion, damaged terminals, or a signal wire rubbed through to ground.
3. Check connector contact and condition, since corrosion or a poor terminal connection can distort the sensor signal.
4. Following the manufacturer's procedure, measure the circuit and check the signal wire for a short to ground.
5. If the wiring tests correctly, test the sender for an internal short and check the control-module input using the manufacturer's procedure.

Common fixes

• Clean or repair corroded terminals in the tank-module connector.
• Repair a Fuel Level Sensor C signal wire shorted to ground.
• Replace the sender if testing confirms an internal short.
• Repair the circuit or module input only if testing identifies the fault there.

Can I keep driving?

The vehicle may be drivable if it runs normally, but the fuel gauge can show an extreme or inaccurate level. Refuel conservatively and do not rely on the low-fuel warning until the circuit is repaired.