P0656 Fuel level output signal: circuit fault

By: Diagno editorial team · Updated: 2026-10-15

P0656 means: Fuel level output signal: circuit fault. A float in the tank measures the fuel level and passes it to the gauge and the engine computer. OK to drive, but have it checked soon. The repair usually costs about €80–400 in Estonia. The most common cause: connector loose, damp or corroded.

What it means

A float in the tank measures the fuel level and passes it to the gauge and the engine computer. The computer found a fault in the electrical circuit: the part, a wire, a connector or a fuse.

What you may notice

• Fuel gauge wrong or jumping
• Engine light on

What could be wrong

1. 1Connector loose, damp or corroded
2. 2Wire broken or chafed
3. 3Faulty fuel level sender
4. 4Engine computer fault (rare)

Repair difficulty: Moderate

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? Until it's fixed, keep track of your mileage so you don't run out of fuel. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the fuel level sender

Standard SAE description: Fuel Level Output Circuit Malfunction