What is a Crankshaft Position Sensor?

What is a Crankshaft Position Sensor?

19th Jun 2017

photo of a crankshaft position sensor, cutaway with numbered diagram of crankshaft position sensor

The average car has around 30,000 individual components (including screws, nuts and other small pieces). While most people are familiar with larger components like the transmission and spark plugs, smaller components often go unnoticed. Nonetheless, the size of a component doesn't necessarily indicate its significance. Even small components like a crankshaft position sensor play a key role in how vehicles operate.

Crankshaft Position Sensor: The Basics

Also known simply as a crank sensor, the crankshaft position sensor is used on petrol and diesel engines to monitor the position or speed of the crankshaft (hence the name). After collecting this information, it sends the data to the car's computer, which it uses to determine the appropriate fuel-to-air ratio, ignition timing and more. 

Prior to its invention, most vehicles required the driver to manually adjust the distributor to a specified timing mark. Thankfully, this tedious process has since been eliminated, as the crankshaft position sensor monitors the crankshaft and sends this information to the vehicle's on-board computer. 

While different vehicles have the crankshaft position sensor in different locations, you can usually find it either around the crank pulley, flywheel, camshaft or crankshaft.

Signs of a Failing Crankshaft Position Sensor

So, how do you know if the crankshaft position sensor in your vehicle is failing? Here are some common signs to look for:

  • Check engine light
  • Heavy vibrations
  • Engine not starting
  • Rough idling
  • Stalling
  • Engine backfiring

According to some mechanics, the most common sign of a failing crankshaft position sensor is the engine not starting when hot. When the car cools back off, however, it starts again with no problem.

Of course, these symptoms can be caused from any number of different problems, only one of which is a failing crankshaft position sensor.

Why Crankshaft Position Sensors Go Bad

Normally, a crankshaft position sensor will last for a while, but there are certain factors that can shorten its lifespan. Exposure to high heat, for instance, is a common reason why this component goes bad. If your car has been overheating, there's a good chance it may have damaged the crankshaft position sensor, in which case you'll need to replace it.

Even if your car hasn't overheated, however, driving for long enough will eventually cause the crankshaft position sensor to go bad. And when it does, you'll need to replace it ASAP.