2004 Toyota Corolla - P0420 Code Cleared - Cleaning the Mass Air Flow Sensor

The check engine light was turning on and off in the car pretty randomly. I used the OBD2 computer and got the code P0420. I looked it up and read on the Toyota Parts Center page "Catalyst System Efficiency Below Threshold". I did a little more research and assumed that it was one of the 02 sensors. I decided to try to clean them instead of replace them, because they're about $70 each. I decided to clean the MAF also, because I had the cleaner. That turned out to be the issue, saved myself some time and money!