P0179 Fuel composition sensor: signal or voltage too high

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

P0179 means: Fuel composition sensor: signal or voltage too high. The computer found a fault in a sensor, valve or control circuit of this system. Drive gently and have the car checked soon. The most common repair costs about €45–90 in Estonia, depending on make and model.

What it means

The computer found a fault in a sensor, valve or control circuit of this system. The signal voltage is too high. Usually a wire is shorted to power, the ground is broken or the part itself has failed.

What you may notice

• Engine light on
• A function doesn't work properly

What could be wrong

1. 1Connector loose, damp or corroded · Wiring or connector repair €45–90
2. 2Wire shorted to power or ground broken · Wiring or connector repair €45–90
3. 3Faulty sensor or valve · Valve replacement €90–180
4. 4Engine computer fault (rare) · Control unit check and software €150–300

Repair difficulty: Moderate

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? Check the connector concerned and see whether the fault returns after clearing it. 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 sensor or valve

Standard SAE description: Fuel Composition Sensor Circuit High Input