How Does an Engine Speed Sensor Work?

Engine speed sensors, which are not to be confused with a vehicle speed sensor, are sensors that are attached to the crankshaft of a car's engine. The purpose of an engine speed sensor is to assess the speed at which the crankshaft spins. These speed sensors are electronic control devices which are used in automotive internal combustion engines. This component sends crucial information to the engine control module (ECM). Crankshaft sensors are used to measure the speed of the crankshaft rotation. The information from a crankshaft speed sensor is used to control the engine management and ignition timing systems. These devices first appeared on engines when distributors were eliminated in the early 1990s. The crankshaft sensor serves the same purpose as the ignition pick up and trigger wheel, which is to adjust the spark timing of the spark plugs. The ignition coil is connected directly to the spark plugs.

How the Engine Sensor Works

The device is basically a metal disk that has a serrated (toothed) circumference. In addition, there's a stationary device containing a magnetic coil, which acts as a standard for the measurement. When the crankshaft spins, induction current is set up around the magnetic coil. The serrated edge of the crankshaft obstructs the produced magnetic field and this is recorded. This is what gives a measurement of the amount of current produced, which is outputted as the speed of the vehicle's engine.

Basic timing information is sent from the crankshaft sensor to the ECM. The engine RPM (revolutions per minute), timing and firing order are determined by the information which is received from the crankshaft timing sensor. The information tells the ECM how fast the engine is running so the ignition can be advanced or retarded accordingly.