|
Re: 2002 Pontiac Montana Error code P0420
You not only have to clear the codes but all the readiness "flags" have to run and pass...if they don't you won't get a sticker...
As for the P0420, the usual culprit is the cat.....however proper testing should be done......it could be the rear O2 sensor, the wiring to it, or a PCM problem, also.....
Usually, you graph the front and rear O2 sensors...if the graphs are mirror images of each other, then the cat is no good....
|