DTC P0301-P0304: Cylinder Misfire Detected: Description
WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) uses information from the Crankshaft Position (CKP) sensor and the Ignition Control Module (ICM) in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way Catalytic Converter (TWC) to overheat under certain driving conditions. The Malfunction Indicator Light (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the PCM detects a misfire rate for a specific cylinder sufficient to cause emission levels to exceed mandated standards, DTC P0301, P0302, P0303 or P0304 will set.