P0388 Crankshaft position sensor: signal or voltage too high ("B")

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

P0388 means: Crankshaft position sensor: signal or voltage too high ("B"). The crankshaft or camshaft sensor tells the computer engine speed and piston position. Don't drive until the car has been checked. The engine could be damaged. The most common repair costs about €45–90 in Estonia, depending on make and model.

What it means

The crankshaft or camshaft sensor tells the computer engine speed and piston position. Without this signal it doesn't know when to fire the spark and fuel. 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

• No start or hard starting
• The engine cuts out while driving
• Rev counter jumps
• Engine light on

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 · Sensor replacement €80–160
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 whether the sensor connector is oily or loose. If the engine cuts out while driving, don't drive until it's checked. 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

Standard SAE description: Crankshaft Position Sensor B Circuit High Input