Fuel Level Sensor "A" Circuit

What it means

The engine computer (ECU) has detected an electrical problem in the fuel level sensor circuit. The fuel level sensor reports how much fuel is in the tank to the gauge and to the ECU (which uses it for evaporative leak tests). The signal is missing or outside the range the ECU will accept.

Symptoms

• Check engine light on
• Fuel gauge stuck, erratic or always showing empty or full
• Low fuel warning light behaves strangely

Probable causes

Most likely first

1. 1Damaged, corroded or unplugged connector
2. 2Open or shorted signal, reference or ground wire
3. 3Failed sensor
4. 4ECU fault (rare)

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the fuel level sensor connector and wiring (on the fuel pump module inside the fuel tank). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the fuel level sensor reading on live data. Watch the fuel level percentage while slowly rocking the car or adding fuel. It should change smoothly.
4. 4With the key on and the sensor unplugged, check for about 5 volts on the reference wire and a good ground (under 0.1 V drop) on the ground wire. Back-probe the signal wire with the sensor connected and watch the voltage change smoothly.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Repair the damaged wiring or connector
• Replace the fuel level sensor
• Clear the code and test drive to confirm the repair