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 ECM. It uses the crankshaft position sensor and the camshaft position sensor signals to compute ignition timing on EI electronic ignition systems.
All distributorless (EI) electronic ignition systems require a crankshaft position sensor. Most cars have either a hall-effect or a magnetic impulse triggering sensor located behind the harmonic balancer or directly on the engine block.
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 and use an ohmmeter to check the resistance with specifications.
The symptoms of a faulty crankshaft position sensor include no start, intermittent start, and poor engine performance.