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Hello and thank you for your question,The code P0401 is set in most cases due to a failing DPFE sensor and usually replacing the sensor will resolve this code. It will not make the engine misfire . The code P0301 and P0306 are engine misfire codes with the code P0301 being the #1 cylinder and the P0306 being the #6 cylinder. This type of misfire can be cause by a failing spark plug and or the spark plug wires and in some cases a failing coil .To determine if its the coil pull the spark plug wire for each cylinder out of the coil with the engine running and see if you have a nice blue spark out of the coil to the wire. If no spark is found then suspect the coil. If you have good spark then suspect the spark plug wire and or the spark plug and if you are replacing one, its best to do both.