P2666 Fuel shut-off valve: signal or voltage too low ("B")

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

P2666 means: Fuel shut-off valve: signal or voltage too low ("B"). The computer monitors fuel pressure in the system. Drive gently and have the car checked soon. The repair usually costs about €60–300 in Estonia. The most common cause: connector loose, damp or corroded. Other possible causes: wire broken or shorted to ground, faulty sensor or regulator.

What it means

The computer monitors fuel pressure in the system. The pressure is wrong, the regulator isn't working, or the pressure sensor reading isn't plausible. The signal voltage is too low. Usually a wire is broken, a connector is loose or a wire is shorted to ground.

What you may notice

• Engine light on
• Hard starting
• Less power or limp mode
• The engine may stall

What could be wrong

1. 1Connector loose, damp or corroded
2. 2Wire broken or shorted to ground
3. 3Faulty sensor or regulator
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? If the fuel filter hasn't been changed for a long time, start there. Check for any fuel leak or smell. Best left to a workshop. It needs a diagnostic tool and experience.

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 regulator

Standard SAE description: Fuel Shutoff Valve "B" Control Circuit Low