P0391 Code: Camshaft Position Sensor “B” Circuit Range/Performance Bank 2

The powertrain control module (PCM) uses the information from the camshaft position sensor to determine the correct injection sequence. Typically found in the engine block or cylinder head, the camshaft position sensor sends a pulse signal to the PCM once it determines that the no. 1 cylinder is in the top dead center position. If the PCM fails to get a signal from the camshaft position sensor, on-board diagnostics will log a P0391 code.

What Does the P0391 Code Mean?

Diagnostic trouble code (DTC) P0391 stands for “Camshaft Position Sensor ‘B’ Circuit/Range Performance Bank 2.”

Camshaft position sensors can be a Hall effect or magnetic reluctance sensor. Either way, they both react to the camshaft position.

After measuring the exact rotational position of the crankshaft, the camshaft position sensor sends a critical data signal that will let the PCM control the fuel injectors and ignition coils, kickstarting the ignition sequence.

Note: The definition of code P0391 might be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P0391 Code?

• Camshaft position sensor failure
• Wiring issues
• Broken tone ring
• Powertrain control module failure or software in need of an update
• A failure of the engine’s timing chain or related components

What are the Common Symptoms of the P0391 Code?

• Illuminated check engine light
• Poor engine performance
• Engine might not start
• Increased fuel consumption
• Stalling

How to Diagnose the P0391 Code

DTC P0391 is a generic powertrain code that can be logged in vehicles equipped with an OBD-II system. While this might be the case, keep in mind that the steps for diagnosis and repair can be affected by vehicle specifications.

Diagnosing trouble codes like the P0391 usually involves using a scan tool and inspecting the affected system for signs of damage. If you think the job is too complicated for you, it’s a great idea to have a certified mechanic diagnose your vehicle for you instead. Otherwise, you can do it yourself.

To help you out, here’s a short video that shows what the diagnostic process for a P0391 code usually involves.

How to Fix the P0391 Code

It can be frustrating and confusing to try and resolve a P0391 code on your own一especially without the right tools and automotive know-how. If you’re not confident with your DIY skills yet, you can always bring your vehicle to the nearest repair shop to have a trained professional perform the necessary repairs. This also ensures that all the steps and protocols for repairing this DTC are followed.

But if you think you have what it takes to do the job on your own, keep in mind that there is no such thing as a magic bullet that will resolve the trouble code for all makes and models. So before you work on your vehicle, make sure to get the right repair manual. Guides like those from Chilton or an ALLDATA subscription contain vehicle-specific repair information, which will definitely come in handy when working on your daily driver.

Fix the P0391 Code With a New Camshaft Position Sensor

Replacing the failed camshaft position sensor is a common fix to clear the P0391 code. When sensors fail, they need to be replaced as soon as possible. Otherwise, your vehicle’s engine might develop more issues and eventually need more expensive repairs. Need a crankshaft position sensor? Look no further than CarParts.com.

CarParts.com offers a wide selection of engine components and sensors that can fix code P0391. These include new PCMs, tone rings, and timing chains. We only source our products from established brands, so you can be confident that they’ve met stringent quality control standards. We also have distribution centers in strategic locations throughout the US, so you can get new components quickly.

Don’t let faulty engine components lead to expensive repairs. Browse our selection of high-quality crankshaft position sensors today!