check engine light on 2006 Lincoln Navigator

P0420 trouble code. Can reset, but comes back on in 2 to 4 days. Trying to figure out if it is a 02 sensor or the catalytic converter.

by in Mission, TX on December 27, 2010
1 answer
ANSWER by , December 27, 2010
To accurately check the O2 sensors will requires a 2 channel lab scope and you need to know the correct / incorrect wave forms of the good/bad sensors under different conditions. I'd leave this to a professional - otherwise you might spend $$$ for unnecessary parts. Zee