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Discussion Starter #1
Believe I'm getting ready to have to replace my cats.

2002 Tacoma DC 4X4, 240k miles. Have been throwing the occasional P0420 code for a couple years now. Only got the code when off roading and driving quite slow, or stuck in stop and go traffic for extended periods (about an hour). Attributed it to the mud caked cat overheating...but have learned a cat that is going bad will start to throw the code in these conditions because it is not getting hot enough to perform properly.

So, I bought an o2 sensor (downstream) and AF sensor (upstream), and will swap those first, but I'm most likely out a cat or two.

Can't pass CA smog as battery was disconnected a month or so ago, and catalyst monitor will NOT reset even though I've put on 300 miles, and have been trying to drive as per the monitor re-set requirements (virtually impossible to do in SoCal). And almost any time I'm stuck in stop and go now for longer than 20 minutes, that P0420 comes back.

Need to pass smog, but I am also going to be selling the truck in the next 4 to 6 months and get into a 2017 Tacoma. So a "cheat" or some other not quite legit fix won't work, as I need to have the truck working properly when I sell.

Truck runs fine, but I just cannot get the catalyst monitor to re-set....especially having to re-set this P0420 code every week or so. Scanguage has shown "not ready" (all monitors not re-set) the entire time, even after driving hundreds of miles with no codes popping up. Will try today to get on some roads and see if I can get catalyst monitor to reset by toyota's guide (drive cycle #4).

What I'm not finding a lot (any) info on, is this:

Is it likely both cats need replaced, or does one typically fail before the other?

Any options other than OEM for CARB and CA compliance that actually work? Looks like I can get a couple Bosal "CARB Compliant" cats either online or through Vatozone, but a couple sellers won't ship these to CA despite being "CA Compliant", and I'm wondering if it is because they just won't pass the smog, and are getting continually returned to them. I realize they may not last ten years or another 150k miles, but I think a couple years' useful life on a vehicle of this age would be reasonable to pass on.

I want to fix it decently before selling (don't want to cheat a new owner), but do not want to sink $1500 to $2k or more into a vehicle I may only be selling for $4k to $5k!
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