had the code p0420.

lasted a couple days. went to fill up the maxima and added lucas upper cylinder lubricant and injector cleaner and the code went away.

Normal? or should I look into seeing if something is wrong?

 

I would be surprised if the Lucas fixed it, but if it did, consider yourself lucky.

 

just be happy it went away, and hope it never returns

 

I wasn't so lucky, so I bought a Y pipe and still haven't installed it.

 

It will be back at some point in the future...can't say when.