P0420 Catalyst System Efficiency Below Threshold (Bank 1)
My check engine light came on last week and this was the code I got. I live very rural and am unable to find someone to check the sensors. I bought the new cat for $1100.00
. Not installed yet. Now the check engine light has gone off by itself.
2007 Forenza. Running great, 120,000 miles on it. I am starting to think it is a sensor and not the cat. i passed smog with flying colors 6 months ago. Any thoughts?