Crankshaft Position Sensor
The crankshaft position sensor is a triggering device for the ignition control module. The engine control module or a dedicated ECU can control the ignition timing. It uses input from the crankshaft and camshaft position sensors to compute ignition timing.
All distributorless (EI) electronic ignition systems require a crankshaft position sensor. Most cars have a hall effect or magnetic impulse-triggering sensor behind the harmonic balancer or directly on the engine block.
Often located behind the harmonic balancer, they can become contaminated by hot engine oil or coolant. Check the waveform with a scanner or oscilloscope for amplitude and frequency. 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.