I am helping a friend out with their car so they can pass emissions. 2017 explorer is throwing a P0420 which I automatically assumed to be a bad cat. They said they just had them replaced a few months ago. Is it possible the previously bad cat burnt out the 02 sensors? Hoping that’s the case or something else is wrong causing it to burn through a cat in a few months. Also, does P0420 indicate it is the bank 1 sensors?
P0420 is related to bank 1. It might be caused by a bad oxygen sensor, a faulty replacement catalytic converter, or exhaust leaks near the oxygen sensor. If you have a scan tool that shows live data, check the downstream sensor on bank 1 to see if it’s working. This will help you find out if the catalytic converter is doing its job. Hopefully, it’s something simple. Good luck though
Thxs for that
i’m gonna to run the scanner tonight and see what I can find.
you’re welcome
No idea what your level of understanding of the system is but there are some guys on YouTube that explain it fantastically. Scanner danner & south main auto have perfect videos on testing such components and what to look for in live data.
first of all is it burning oil???
Unless the old cat(s) rusted out, they are a lifetime part, were probably fouled by an engine problem, and that engine problem was not fixed, so the new cats are now fouled too, or the O2 sensor on that bank. No a bad cat would not burn out an O2 sensor, but the same thing that caused the cat to go bad (if not rusted out, as already mentioned) can foul the O2 sensor, the old one, or a new one as it really should have had a new O2 sensor put in with the new cat.