P0391 Camshaft position sensor: reading or operation not right ("B", bank 2)

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

P0391 means: Camshaft position sensor: reading or operation not right ("B", bank 2). 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 €80–160 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. There is a signal, but the reading or operation isn't plausible. The cause may be the part itself or a real mechanical fault. Bank 2 is the side of a V engine without cylinder 1.

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. 1Faulty sensor · Sensor replacement €80–160
2. 2Sensor connector or wire (oil or heat damage) · Sensor replacement €80–160
3. 3Damaged reluctor wheel · Sensor replacement €80–160
4. 4Chain or belt jumped · Timing belt or chain replacement €400–800

Repair difficulty: Moderate

What you can check yourself

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 sensor on the diagnostic tool and compare it with other sensors
2. We check the connector, supply and ground
3. We repair the wiring or replace the sensor

Standard SAE description: Camshaft Position Sensor "B" Circuit Range/Performance (Bank 2)