I got an error code P0420, catalyst system efficiency below threshold (Bank 1) Where should I start checking?

 

There is a test in the Ford manual that is close to 15 pages long. The easiest thing to do is to erase the code and see how long it takes to come back. We do that often and some never come back. Most of the time though, if the P0420 is set, the converter is shot. Sorry.

 

Thanks, I erased the code yesterday and its still not back on......I'm not hearing anything that would lead me to think its a shot converter.....could be the o2 sensors, I take it there are only two????????? An upper and lower.

 

Don't replace the sensors. If the converter's chemical balance has failed, you will not hear any noise. If the O2 sensors are bad, it will give a different code. The P0420 is for the converter is below efficency level.

 

The check engine light has still not come back on.....will wait and see