Camshaft Position Sensor

It takes pinpoint precise timing for an engine to run, and the camshaft position sensor is integral in making it happen. Engine timing relies on the camshaft being in a specific position to indicate when it’s time for a spark plug to fire. If the timing is off just a fraction of a second, your engine might not run efficiently or at full strength, or it might not run at all! It’s up to the camshaft sensor to identify to the onboard computer how the camshaft is oriented.

How Do Camshaft Position Sensors Work?

The camshaft position sensor, often simply called the cam sensor, is a type of Hall effect sensor. It detects a magnetic field and the strength of the field. Positioned very near to a ring gear on the camshaft, it detects how the camshaft is positioned as it rotates. As the cam rotates, different points on the ring gear cause the sensor’s voltage to vary. This data tells the car’s onboard computer how the camshaft is positioned in the engine so the computer knows cylinder #1’s top dead center (TDC) position. All timing is relative to TDC.

The data from the camshaft position sensor alone isn’t enough to allow the engine to run, however. The onboard computer also requires data from other components like crankshaft position sensors, mass air flow sensor, and several other sensors and systems. Using the camshaft sensor’s data along with other sensors, fuel is injected into cylinders at exactly the right moment and the spark plug fires and ignites the air-fuel mixture.

Symptoms of a Failing Camshaft Position Sensor

Although tucked out of sight and securely fastened to the engine, the camshaft position sensor can be prone to fail. After all, it’s a delicate plastic housing with two wires and a sensor head the size of a thumb that fits into the cylinder head. Failures can include a cracked plastic housing, an internal short in the circuit, degradation or corrosion in the connector, or mechanical damage or impact to the sensor head.

How can you tell that the cam sensor is faulty? There are a few common symptoms that can lead you to diagnose the camshaft sensor as the culprit. You could have difficulty starting the engine since the onboard computer is having a tough time identifying TDC. The Check Engine Light may come on with a P0340 fault code in the powertrain control module. You might also feel a loss of power or stalling, poor fuel mileage, or your car could go into a protective mode referred to as ‘limp-in’ mode that limits its performance.

How to Replace a Camshaft Position Sensor

Like other automotive sensors, changing the camshaft position sensor is typically a short, straightforward process. The biggest challenge is an accurate diagnosis. A new part ranges from $30 to $150 or more, depending on the car you drive.

At AutoZone, you’ll find the replacement parts and tools to change your cam sensor. Find the right sensor for your application by filtering by year, make, model, and engine size, then choosing from popular brands. We have What It Takes To Do The Job Right, and you can get it quickly with Free Next-Day Delivery on eligible orders, or pick it up sooner with Free In-Store and Curbside Pickup.