A misfire is caused by a cylinder that is not firing as it should. In this case, the DTC code P0307 OBD2 is stored due to an ignition failure in cylinder 7.
Different manufacturers implement OBDII requirements. One of these is the misfire monitor, which is based on changing the crankshaft speed. To determine the crankshaft speed, the PCM uses the information provided by the Camshaft position sensor (CMP) and the Crankshaft position sensor (CKP). When a cylinder fails, it momentarily slows down since the CKP and CMP sensor signals are monitored by the PCM, which can calculate when an ignition failure occurs.