Repair 7

What Is the Purpose of a Crankshaft Sensor

Sophisticated computers that continuously adjust critical engine parameters control almost all modern car and truck engines. The crankshaft sensor is one of the numerous sensors that feed information to the computer.

Function

The crankshaft sensor sends information to the engine computer about the precise position and speed of the crankshaft. Because the crankshaft is attached to the pistons, information about its position allows the computer to determine the relative positions of all critical engine components, including pistons, belts and valves. This makes it possible to time the injection of fuel and the spark plug ignition for optimum performance and fuel economy.

Principle of Action

The crankshaft sensor consists of a metal disk positioned on the crankshaft and a detector that covers a magnetic coil. The metal disks movement past the coil causes a disturbance in the magnetic field, creating a stream of electric pulses that the computer uses to determine the speed and position of the crankshaft. The sensor does not produce direct data about the location and speed of the crankshaft; it sends raw data to the engine computer, which then calculates the desired values.

Malfunction

A malfunctioning crankshaft sensor can cause various disturbances including extended crank time during start-up, rough running, bucking, compromised fuel economy and stalling. If your vehicle is equipped with an on-board diagnostic computer, a malfunction of the crankshaft sensor will trigger an error code to inform you about the problem.