Just like the name indicates, the crankshaft position sensor monitors the rotation speed and position of the crankshaft. The crankshaft is what turns the engine’s piston power into a force that can actually move the vehicle. Its position must be tracked in order for other parts involved in the engine’s operation to work properly, such as ignition timing, fuel injection, and spark plug firing sequence. In other words, if the crankshaft position sensor – also known as an engine speed sensor – malfunctions the engine will not run correctly.

This sensor is typically comprised of an inductive coil along with magnets. It may be located on the flywheel, main crank pulley, or the crankshaft. The sensor may malfunction due to damage to its physical structure from wear and tear, magnet problems (the magnets that help it function can also attract metal shavings from other parts), or because of wiring problems (wires connect the position sensor to a power source and the ECU – engine control unit).

Signs your crankshaft position sensor needs replacing

  • The Check Engine light comes on, particularly after the car has been running for a while. This happens due to the sensor malfunctioning when it gets hot.

  • The car will start sometimes and not others. Eventually, if the problem is not fixed, the engine will not turn over at all.

  • The engine will misfire or hesitate on acceleration. This is due to miscommunication between the cylinders and the car’s computer.

  • You may feel vibration when the engine is running or experience general abnormal engine behavior.

It’s important to pull codes from the vehicle if you have a code reader, or else have a shop do it, because many other part malfunctions can cause similar symptoms to those from a broken crankshaft position sensor. If this important component is the problem, there are some important things to consider when buying a new one.

How to make sure you’re getting a good quality crankshaft position sensor

  • Make sure you’re getting the correct kind for your vehicle – there are two types - magnetic field sensors (called variable reluctance), and Hall Effect. Both use magnetic fields to measure crankshaft position, but operate in slightly different ways.

  • Choose a replacement crankshaft position sensor that includes an O-ring if applicable. You will generally need the ring if your sensor is mounted on the engine, so make sure all necessary components are included.

  • Look for a sensor with high heat resistance – preferably up to 300 degrees F. If the heat rating isn’t high enough the part could crack or melt. Whether you perform the switch yourself, or have a professional mechanic put in your new crankshaft position sensor, the part itself is affordable and fairly straightforward to replace.

YourMechanic supplies top-quality crankshaft position sensors to our certified mobile technicians. We can also install a crankshaft position sensor that you've purchased.
Click here to get a quote for a crankshaft position sensor.

This article originally appeared on YourMechanic.com as How to Buy a Good Quality Crankshaft Position Sensor and was authored by Valerie Johnston.


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