DTC P0300: Engine Misfire Detected: Description

The Crankshaft Position (CKP) sensor sends 58 pulses per crankshaft revolution to determine the position and RPM of the engine at various degrees of rotation. The crankshaft reluctor wheel contains 20 notches for every 120° of crankshaft rotation except for two missing notches used to detect cylinder #1 TDC. The ECM bases misfire diagnostics on the principal that at a given speed and load, the time to pass 20 notches on the crankshaft between firing events should be below a certain threshold. If the time to pass 20 notches exceeds a calibrated time, a misfire is detected on the previous cylinder. Under certain conditions, the ECM will monitor misfires in both 200 (catalyst damaging counter) and 1000 (emission related counter) crankshaft revolution tests. If a certain number of misfires (greater than 30 out of a 1000 revolution test, or greater than 45 out of four consecutive 1000 revolution tests) occur over a certain number of engine revolutions, DTC P0300 will set. The MIL will then be commanded ON after two consecutive drive cycles if DTC P0300 fails again. The MIL will turn OFF after three consecutive passed drive cycles meeting the same criteria or 80 passed drive cycles if the criteria could not be met. DTC P0300 sets if specific or random cylinder misfires have occurred for a certain length of time.