here's how it started. my cel was showing bc of the P0420 code. did my research and know that its bc of exhaust leak, o2 sensor, or bad cat. i have no exhaust leaks, great o2 sensor, and a used but good conditions magnaflow hfc. cel is still on. I bought some non foulers and installed them( and uppluged the battery). i putted both of the non foulers on, and drove for 200 miles w/ no cel on. i went to get the car inspected. As they were inspecting it, their scanner couldnt read or find my o2 sensor, and i got a (not ready for emission test). whats going on? after i got out from the inspection, i took out one of the non foulers and left the other one on the o2 sensor (just to see if it makes a different). I have heard of people in nc passing with nonfoulers. But how come that scanner cant read my o2 sensor? they told me to drive around more, but what if their scanner cant read my o2 sensor at all? its getting me mad.

any suggestions? thoughts? advices?