Crankshaft Sensor
WARNING: This page is about a different car, the 1997 Lexus SC 300. However, it is still accessible from the selected car via links, so may be relevant.
Crankshaft sensor contains a pick-up coil. A signal plate (rotor) is mounted on the crankshaft pulley. As the crankshaft rotates, protrusions on the signal plate pass near the pick-up coil. This induces AC voltage in the pick-up coil. The ECM senses the AC voltage, and uses it to determine engine speed and crankshaft position.