Close-up of a camshaft position sensor

What Is a Camshaft Position Sensor And What Does It Do?

Modern engines are impressive machines made up of individual parts interacting with precision, which is necessary for top performance, efficiency and safety. Without it, you don’t get much. Many components are responsible for keeping everything humming along, but an important one is the camshaft sensor. But, what is a camshaft position sensor, and why is it so important?

A Time for Timing

Gasoline combustion engines have very specific needs for air, fuel and spark in order to run as designed. These three elements must be available at the right time and in the right quantity for efficient combustion. If the timing is too far off or if one piece is missing, you may not get any combustion.

An engine’s precision is enabled by a system of car sensors that monitor components and conditions and interface with the electronic control unit (ECU), the vehicle’s main computer. The ECU receives input from sensors and makes an immediate call based on programming. It then sends a signal to an actuator that changes or maintains a condition, including air, fuel and spark, to reflect information from the sensors. If there is a mechanical problem and one of the components is faulty or broken, the sensors will let the ECU know to either adjust or alert you.

camshaft sensor on notebook paper

Smart Cams

The camshaft and crankshaft are two of these important components. The camshaft controls the position of the inlet and exhaust valves, while the crankshaft controls the location of the pistons themselves.

If a camshaft controls those valves, what is a camshaft position sensor, and why is it necessary? Camshaft position sensors monitor the camshaft’s position and send information to the ECU about when each valve is open on a particular cylinder. They work closely with crankshaft position sensors to paint a more complete picture for the ECU.

Together, the information from these two sensors shows when a piston is at the top center for a potential intake stroke and confirms that the valves are aligned to deliver air and fuel. Basically, camshaft and crankshaft position sensors work together to show the computer when the conditions are right for intake, compression, combustion and exhaust.

Sensory Deprivation

A camshaft sensor problem will usually trigger the check engine light. From there, you can do a diagnostic scan to suss out a camshaft issue, but it won’t tell you whether the problem is the sensor or the component it’s monitoring. That will take further digging.

You may additionally notice problems with drivability. The engine may stutter or surge, use more fuel than usual, have poor acceleration, stall or not even start at all. These are all signs of a problem with the camshaft, but again, you’ll need to take a closer look. A failing sensor or glitchy ECU can also cause these problems, and sensors are much easier to change than camshafts, so have a mechanic check it out if you’re not sure.

Your ECU should let you know when something is amiss, but if you notice problems, get it checked out sooner rather than later. Camshaft issues only get worse with time and can cause bigger engine problems down the road.

Check out all the relays, sensors and switches available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on camshafts, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Flickr.

about author

Blair Lampe

Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter.  In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck.

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