It's been a few days and no CEL has returned.

 

When I first started getting my P0420, I would clear it and it took two months to return. The interval kept dropping until it would come back on within a few days (presumably the two-trip detection thing). I kept notes; it took almost a year and 10k to become unbearable. As I was coming up to inspection date, I changed the rear O2 sensor and CEL has not been seen since (25K and 2 years).

My guess is that a degraded rear sensor can sit borderline and not set codes unless some more stressful set of events occurred. I remember it seemed to go out on trips as I was always waiting to get home to my BR-3 to find what code it was and then reset it.

So don't be surprised if it takes a month or two and then comes back. If it is just a degraded rear sensor, it will have no effect on performance or drive-ability.

 

Aftermarket or "cheapo" catalytic converters are garbage!

 

I beg to differ. Got mine from carparts.com for $40+s/h. I had to have it welded in and never had a problem in over 2 years.

 

I think the issue here is that after 2000 Toyota did something to their emission system, as I know people with '99 and up having issues.

 

Mine tripped about halfway through my trail run so I think I'll just replace the rear sensor in the next month or so and avoid the inevitible.

 

I got that code to pop up yesterday and I have had big exhaust leak at the manifold on the 3rz-fe. Ordering the mini-header today to see if it will fix.

 

i have a 2000 2.7 i keep getting the 420 code off and on last few months .

i would clear it and it would stay off for a week or 2 .. i just swapped out the cracked stock iron manifold and replaced it with the oem shorty header with all new gaskets
.. my wife drove it just fine for the week and it threw the 420 code again .

im still running the stock exhaust so maybe its hosed and needs replaced ? im going to try and find a oem o2 sensor see if it helps 1st .. dang cats are not cheap !! atleast with the options i have here in north pole ak .

 

Got the same code on my 98 Monte Carlo about 8 months ago. Owner's manual says it can be from bad gas and to try a different brand. If it was the gas, the code should clear itself with about a half-tank full of good gas ran through it or few weeks driving. Well, it didn't. So I used a buddies OBD-II scanner to clear it. Looked into a new cat for it afterwards. But it hasn't been back yet. Knocking on the wood....<knock><knock>!

Just thought I'd mention the gas thing. I didn't see it mentioned but maybe I missed it?

 

Well,it's 3 months later and no CEL has popped up and my truck is running normal and had the code cleared from memory at Pepboys and they did it for free. I've read a few other things that people had it pop up after off roading so maybe a sensor was just a tad loose and I went under and tightened both of them but so far so good.