I am in same predicament. My 2001 Monty XLS CEL comes on, and P0431 is on my OBDII reader. I put Pass4Sure in the tank, and right after 60 miles, the darn CEL came on... right before I was going to take it to CA emissions test. All I really want to do is get the light to turn off for about a week/hundred miles and take it to emissions so it will pass. CA emissions, since she is 2000 or newer, only has to be inspected and have the computer read. They don't hook it up to the dyno.

How can I get it to turn off for just a week - long enough to get her inspected? I don't really want to pay 1400 dollars for a new Cat, only to have the CEL come on three months later with some other issue.

I saw a post about seafoam in the oil and PCV. Not sure what he was referring to, since he had sport model. Does anyone know about that? Surely it would not hurt to try. And when you guys do that, do you reset your codes, or remove the battery to do so. Can they tell you reset your codes at the smog inspection place?

 

We had that problem for a long time until we finally replaced the O 2 sensor. However, what usually worked for us short term was to use CataClean. $25 bucks at AutoZone, works for at least a month or so. Good luck!

 

I also found the Y pipe online for 700 dollars. I had it replaced - that was 200 dollars at local shop.


I did use Cataclean, and soaked PCV valve in Seafoam over night. Also put Seafoam in gas tank.


The CEL light went off for a week more, before I had the cats replaced. I'm in CA, and it passed smog. But since I had the Y in my living room, I paid them to replace it.


Now my Monty is throwing a P0155 code. Hunter says that is the front O2 sensor, driver's side.


My suggestion... if you have to pass smog, and that's all you care about, try the cataclean and seafoam and be done with it. But if the CEL bugs you, then replace the cats. My Monty also has 175k on it.


Anyone have the PN# for the O2 sensors?