The main function of CMP is also called "cylinder recognition sensor", or less commonly used "phase detector", its main function is to determine which cylinder should be supplied with fuel next. In fact, the CMP sensor provides the PCM (Powertrain Control Module) with data on the engine ignition sequence, but please note that the PCM always refers to the time when cylinder #1 is close to TDC to calculate the fuel delivery time.
However, in some applications, the PCM does not need to identify cylinder No. 1 or the firing sequence because this information is obtained from a sensor that identifies the position of the crankshaft and/or other rotating components relative to the cylinder's TDC position.
Why do you need a CMP sensor?
In order for modern engines to run smoothly and efficiently, the engine management system needs to start, monitor, control and regulate multiple processes at the same time. Usually, these processes include ignition timing, fuel injection timing control and adjustment, as well as injector pulse width, valve/camshaft timing, etc., including the calculation of the best time to purge the EVAP system.
Although many sensors contribute to the overall engine management strategy at any given moment, using one sensor, in this case, the CMP sensor provides the main input data and can measure all other inputs, thus providing a simple, cost-effective solution which is a reliable way to ensure that the engine always runs efficiently.