Crankshaft Position Sensor
The crankshaft position sensor serves as a triggering device for the ignition control module. Most late-model vehicles have this module located inside of the PCM. The crankshaft position sensor signal, along with the camshaft position sensor's signal, is used to compute ignition timing on EI electronic ignition systems.
Most cars have either a hall-effect or a magnetic impulse triggering system. A permanent magnet crankshaft position sensor is located behind the harmonic balancer or directly on the engine block. All distributorless (EI) electronic ignition systems require a crankshaft position sensor.
Because these sensors are often located behind the harmonic balancer, they can become contaminated from hot engine oil or coolant. Check the waveform with a scanner or oscilloscope for amplitude and frequency. Use an ohmmeter to check the resistance against specifications.
The symptoms of a faulty crankshaft position sensor include no start, intermittent start, and poor engine performance. This sensor affects fuel and ignition timing.