My check engine light has been coming for past 3 weeks. The error codes are always P0420.Once I also got the P0300 ( misfire) I did the major service maintanence yesterday at a local Toy dealer for about $250 but that didnt fix the problem ( I was assuming changing the spark plugs might help P0420 but looks like the P0300 is gone ). I checked and the code mentions "Catalyst efficiency below threshold in Bank 1). Anyone got this before and how did you fix it? I am scared I will be poorer by a few more dollars.
I have a 99 4 cyl Camry..