Engine Speed Sensor: Description and Operation

ENGINE SPEED SENSOR

The periphery of the flywheel/carrier plate is provided with a series of holes. As it passes, each hole induces a voltage in the pick-up coil of the Engine Speed (RPM) Sensor. The passage of several holes generates an A/C signal whose frequency is a function of the number of holes passing per second and whose voltage can vary between 0.1 Volts and 55 Volts, depending on the engine speed (RPM) and temperature. The voltage increases with RPM and temperature, while the frequency also increases with RPM. The ECM determines the RPM and angular position of the crankshaft by detecting the voltage pulses.

The pitch between two of the holes at a position corresponding to 90° before TDC is greater. The voltage pulses are interrupted as this point passes the sensor, enabling the ECM to determine the angular position of the crankshaft.

The engine will stop if the signals from the sensor to the ECM are lost.

The sensor consists of the following components:
^ Housing (1)
^ Permanent magnet (2)
^ Coil (3)