Burning through catalytic converters

Long time lurker, first time poster. Grateful for all the past help this forum has been, and hoping for some more insight.

2006 Tacoma with 150k miles located in San Francisco Bay Area, California.
Bought with 36k miles on it. Started having check engine light codes around 60k, at 78k got Toyota to replace my bank 2 cat on warranty. I’ve had issues with the cat code since very shortly after, but warranty on emissions up at 80k. Over the last 6 years (since having bank 2 replaced,) the code would always come in after filling up with gas. when I hit 3/4 tank of gas the light would go off, then come back in as soon as I hit 1/4 tank, and cleared for a month or so after I got a new gas cap, so I was always able to smog it as long as I planned around my fill ups. The last 3ish months the code hasn’t cleared at all, and I have to smog by April 30th, so I took it in to be looked at and have my 150kmi service done, and the code pulls cat bank 1 not working and now needs to be replaced. Has anyone else experienced emissions issues like this? When it’s the O2 sensors out, will it still throw the cat code, or should I be fairly confident it’s the cat? I won’t be super happy with the $2500 bill (including my 150k service,) if the code doesn’t clear. Thanks in advance!

 

Yes a bad o2 or bad cat can throw the code. To check if it's the sensors, you can switch the o2 sensor to the other bank and see if the code follows. If you get a new code after the switch for the other bank, then you can be confident it's the sensor. if the same code is thrown from before, after the switch, then both sensors are reading correctly and it's the cat that is not working properly.
reset the codes after the switch and wait for a new code to pop.

 

Update to add:
Shop called and said testing indicated bank 1 cat not working. They have a tech who has my exact truck, and has never had car issues. Said they checked computer trends for fuel usage and ratios, and can’t figure out any reason I would be going through cats every 70-80k miles.

 

Are you burning oil?

Edit: This probably wouldn't cause it, but just for the sake of asking. When you fill up, do you stop when the pump stops? Or are you one of those people who keep trying to fill it up more and more.

 

No burning oil that I’m aware of. Haven’t seen a drop in level at all, smell, etc.

 

Just from how you had to fill up with gas, and why I was wondering if you over fill, is that can backup into the evap system. Cats can only be killed a few ways, excessive oil, gas, or physically bashing them. I only have a 1GR-FE manual, but you're not getting any evap codes? I would imagine it's similar enough https://smallpdf.com/result#r=3f45d02edf1e57bd7959aa3905b1ef59&t=share-document

Edit: If you read that, I'm wondering if the cut off valve is stuck open.

 

My bet is you have a o2 sensor that needs replaced.

 

You have any pissed off ex's running around? Sorry man that is not a good problem to have, especially in CA.

 

You can also get the URD O2 simulators if passing smog is your only concern, or find a friendly smogger

 

Time for some headers.

 

Something doesn't add up. To burn that many cats and even o2's.

Just to start, bank 1 o2 is more or less the only o2 that matters. Bank 2, just checks for emissions, but will not make any fuel changes. It's more or less just there to turn the CEL on letting you know there's an emission issue. A straight up bad bank 2 o2 will not change anything as far as drive-ability goes. That's why you can just bypass them with a few resistors to make the ECU happy thinking it's all good.

One thing I did not think about, would be not so much the cat, but the rest of the exhaust. Is the muffler plugged? Possibly you have excessive back pressure?

OP said that they mechanic checked the AFR etc. I would assume along with this they checked for vac leaks, ECT, MAF, anything that's going to effect the AFR. *assuming* this was all done, and no apparent issues were found. There's something missing.

Since OP mentioned a lot about filling up, and not being able to go past 3/4 a tank, I'm really leaning towards and evap problem. If OP could post codes, it would be easier than guessing.

This is the first video I found, but he does a decent job of going over the parts/locations https://www.youtube.com/watch?v=6aWmTuaCN0A

Again, going on the information given, I would start looking at the purge valve. This will shove more fuel fumes (even cold) into the system. Excessive fuel/oil will burn out a cat. I would be curious if the tech went though the evap test procedure, tempted it, or could even note the color. It's been way too long, but I thought it should be something like 1600 degrees. Once you see purple, it's probably toast.

Last bits to add, the best way to wreck your evap system, is shoving more gas in your tank after it shuts off. Don't. Do. That.

Edit: link was pulled, re-uploaded https://gofile.io/d/cRcjLp

 

too much heat can kill cats
like if the engine runs rich for some reason
burning oil can kill cats

o2 sensors can fail

dealer scan tool probably better than some cheap OBD2 reader

makes no sense

 

My mistake, I'm just so used to i4 or straight 6 with one pipe. I mean bank 1/2 as in pre-cat post/cat.

 

What's the code that keeps coming back?

I've got almost 350k on my truck with original cats.

I did have a P0420 code once and that turned out to be a gasket that was bad.

Somebody's missing something imo....

Good luck in getting it figured out.