What is the Function of a Crankshaft Position Sensor?

The crankshaft position sensor, in case you don’t know is an electronic device that is vital to the functioning of a car. It is located in the engine of the car. It registers the rate of spinning of the crankshaft. This sensor then passes the information to the ECU and decided optimal fuel injection and regulation of ignition. It is the location of the crankshaft that determines the effectiveness of the gathered data. This is why the sensor is located either next to camshaft or the crankshaft itself.

If we try to explain it in simpler words, the crankshaft position sensor monitors within the engine, the location of the camshaft. The information that it gathers thus, it uses the same to optimize the timing of fuel injection in the engine. In case this sensor malfunctions, the computer will be unable to make fine adjustment to fuel injection and the performance of the engine will dip.

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How Does the Crankshaft Position Sensor Work?

Here are a few ways in which this sensor functions. Let’s take a look.


If you look at the crankshaft, you will find a powerful magnet next to it. You will also find that there are steel pins or pegs arranged at regular intervals around the crankshaft.

Crankshaft position sensor monitors
Lean about crankshaft position sensor (photo source: BMW Owner Blog)

This magnet constantly radiates a magnetic field that is steady. As the engine starts and the crankshaft spins the steel pins around the shaft rotate around this field. This causes fluctuation in the field, thus producing an AC (alternating current) signal. This further signals the engine management unit (engine computer) to decipher the speed of rotation. In turn, the EMU is able to calculate the position and the pace of the camshaft to further optimize fuel injection and ignition.


The way modern cars are, we must learn one thing. The engines will give us an efficient performance only if the internal parts are moving at a particular recommended speed. It is only once the crankshaft position sensor senses the rotation of the crankshaft inside the engine that the on-board can make use of the information that the sensor sends to it. This is when the computer will make small adjustments/fine-tunings in to the engine to increase its efficiency.

Consider the cases when you are moving full-throttle. The constant throttle in modes like cruise mode or sports mode, the computer needs to make these fine adjustments to the engine in order to change the speed. The computer will ensure that it constantly checks the rotational speed of the crankshaft, compares it to the ideal range, and make speed adjustments accordingly. This adjustment can be in terms of both increasing and decreasing the speed.

What Happens when the Crankshaft Position Sensor Malfunctions?

Malfunctioning of Crankshaft Position Sensor
How to maintain Crankshaft Position Sensor (photo source: thxsiempre.blogspot.com)

If you need to keep your engine performing well, it is imperative that this sensor stays in top condition. Any defect in the sensor will result in the communication of incorrect data to the engine management unit. The engine, when performing on the basis of this data will not perform optimally. It may even go as bad as making the car stall. The reason is that the EMU will start depending on its own memory to ensure fueling and ignition, which by the way, cannot be optimal. So, diminished engine performance could actually be one of the symptoms of crankshaft sensor failure.

Thus, the crankshaft position sensor plays a very important role in ensuring the performance of the engine and adding to its efficiency. Follow the maintenance tips recommended by your automaker to keep it in a great shape.