2003 chevy cavalier

Question

Get p0300 code replace emission control module about every 3000 miles

Answer 1

P0300 Random misfire

P0420 Catalytic below threshold

When there is a misfire condition this is where the catalytic cannot function and perfrom well. so any mifire condtion will set a catalytic code. Misfire are mainly ingition related such as sparkplug wire and sparkplugs, If you are replacing igntion moduel every 3000 miles what type of sparkplug are you using? The sparkplug well should not have any oil leakage in there . If there is a poor ground connection of the ICM (ignition control module) that is more of there reason for its early failure.