Buy crankshaft position sensor: detects crankshaft and engine speed and provides reference signal for ECU to determine ignition timing and operating sequence. The function of crankshaft position sensor is to determine the position of the crankshaft, that is, the Angle of the crankshaft and the engine speed. It usually works with a camshaft position sensor to determine the basic ignition moment. We all know that the engine starts firing at the end of the compression stroke, so how does the engine computer know which cylinder to fire? Is calculated by the signal from the crankshaft position sensor and the camshaft position sensor, through the crankshaft position sensor, you can know which cylinder piston is in the TDC, through the camshaft position sensor, you can know which cylinder piston is in the compression stroke.