DTC P0300: Random / Multiple Cylinder Misfire Detected (TO 12/2010); DTC P0301: Cylinder 1 Misfire Detected (TO 12/2010); DTC P0302: Cylinder 2 Misfire Detected (TO 12/2010); DTC P0303: Cylinder 3 Misfire Detected (TO 12/2010); DTC P0304: Cylinder 4 Misfire Detected (TO 12/2010); DTC P0305: Cylinder 5 Misfire Detected (TO 12/2010); DTC P0306: Cylinder 6 Misfire Detected (TO 12/2010): Description

When the engine misfires, high concentrations of hydrocarbons enter the exhaust gas. High hydrocarbons concentration levels can cause increase in exhaust emission levels. Extremely high concentrations of hydrocarbons can also cause increases in the three-way catalytic converter temperature, which may cause damage to the three-way catalytic converter. To prevent this increase in emissions and to limit the possibility of thermal damage, the ECM monitors the misfire rate. When the temperature of the three-way catalytic converter reaches the point of thermal degradation, the ECM blinks the MIL. To monitor misfires, the ECM uses both the VVT sensor and the crankshaft position sensor. The VVT sensor is used to identify any misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed. Misfires are counted when the crankshaft rotation speed variations exceed predetermined thresholds. If the misfire count exceeds the threshold levels, the ECM illuminates the MIL and sets a DTC.

When multiple DTCs for misfiring cylinders are set, but DTC P0300 is not set, it indicates that misfires have been detected in different cylinders at different times. DTC P0300 is only set when several misfiring cylinders are detected at the same time.