DTC P0301-P0304: Cylinders No. 1-4 Misfire Detected: Condition

WARNING: This page is about a different car, the 2002 Mazda Protege5 and 2002 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.

PCM monitors Crankshaft Position (CKP) sensor input signal interval time. PCM detects a misfire in a specific cylinder by calculating change of CKP interval time for each cylinder. While engine is operating, PCM counts number of misfires that occur during 200 crankshaft revolutions and during 1000 crankshaft revolutions in order to calculate a misfire ratio for each crankshaft revolution. If misfire ratio exceeds a preprogrammed criteria, PCM determines that a misfire has occurred which can damage the catalytic converter and will set a DTC. DTC P0301 is set when cylinder No. 1 misfire is detected. DTC P0302 is set when cylinder No. 2 misfire is detected. DTC P0303 is set when cylinder No. 3 misfire is detected. DTC P0304 is set when cylinder No. 4 misfire is detected. This is a continuous monitor. MIL is illuminated when PCM detects malfunction during 2 consecutive drive cycles. Possible causes are:

Fuel injector malfunction.
Low engine compression.
Poor connection or wiring malfunction.
Secondary ignition system malfunction.
Spark plug malfunction.
Vacuum leak in intake-air system between dynamic chamber and cylinder head.