2004 Tacoma V6 Catalyst not ready

10.5.22 update: not only is the cat still not set, but the computer is now spitting out a 0420 code. Truck has new cats, both for fore and aft sensors and a new MAF sensor. What's next? exhaust leak? new plugs/wires? Really, really frustrated.

 

Man that sucks. P0420 usually means catalyst is bad i.e. bad cats, but you have brand new ones....I wonder if there's a leak where they were installed? If there is then that would trip up the rear O2 sensor into thinking the cats aren't performing properly

An exhaust leak is my best guess unless there is something inherently wrong with the new cats that were installed

 

Where did you buy your "DENSO" sensors? There are a lot of fakes out there and the Tacoma is a picky truck with sensors.
Also, I think the 50-state Tacoma requires a specific model depending on automatic vs manual trans.

I had an intermittent P2238 code on my 2003 when I was out in CA and reset it. It came back a few times and I finally bought a DENSO sensor pre-COVID when fakes weren't as plentiful.
193k it first popped up on the highway. Cleared it.
198k it came back in Rocky Mountain National Park an hour into a drive, so everything was warmed up and should have been functioning properly.
205k I replaced the bank 1 sensor 1 with

$146 Denso 234-9001 Upstream Air Fuel Ratio Oxygen Sensor with 10.6” 4-Wire Harness, for Auto Trans Equipped Vehicles

Denso 234-9001
Sold the truck with 235k. Code had not come back.

 

I decided to crawl under and see what cats my mechanic purchased and installed. They both appear to be Magnaflow, California compliant. My motor is the 3.4 V-6, emissions test group is VRM according to the label in the engine compartment.
Front cat is carrying a part number of 444759. However, that number is not shown on the Magnaflow site for the VRM. It does appear for the VRH series emissions test group.
The rear cat's part number is 441005. this appears to be a California compliant, but universal cat. It's welded in. The notes on the Magnaflow site say Lev1 Lev. That does not appear on the front cat's website. This one also is listed in the VRH emissions test group.
It seems to be incorrect cats, yes? Will the different emissions test groups (vrm vs vrh) be noticeable to the computer?
Thanks.

 

JasonLee-my sensors are real denso's as far as I can tell; I clicked the link on the Denso site. I purchased the precious set from rockauto and they worked fine for 80k miles.

 

Update: I'm picking up the truck today. Finally got the mechanic to install the correct cats for my truck's engine family. So I now need the computer to monitor the cat; What's the best way? Do I reset my computer (delete the 0420 codes) with the scangauge, un-plug the battery or will the computer update itself? Provided the wrong cats are the reason for it not setting of course... But with a new mass airflow sensor, O2 sensors and cats, not sure where i'd go next. I'm going to try the drive in procedure Saturday morning before traffic. Thanks again.

 

The computer will run the emissions cycle on it's own, but if you disconnect the battery or use your scangauge to "clear all codes" it will reset the monitors and they will run their cycle from there

 

If everything is good, the cycle should complete within a couple hundred miles of driving or less. Depends on driving conditions and all the stuff we talked about earlier in the thread, but hopefully it sets quickly for you after all this work


Mine haven't reset since I cleared a code a few months back and I suspect new cats are in my near future once again My aftermarket Magnaflows lasted about 6/7 years

 

Update: finally! The scangauge said READY this morning. I didn't drive the truck for a couple weeks until I went to DMV and picked up some single day temp tags. I'd already used up most the 60 day extension before I discovered the incorrect cat problem. Without any real proof of what worked; correct engine family cats and both sensors were what it took. I stopped tying to do the specific drive pattern out of frustration. Now to see if it runs cleanly enough to pass emissions.

 

Congrats! You should be fine, 2000+ year vehicles do not have to do a sniffer/dyno test in CA...as long as your monitors are all green and good to go, and you have no reason to fail the visual inspection, you will pass.

1999 and older vehicles have to do the dyno/sniffer test where they measure the levels of certain exhaust gases and can fail the vehicle even if the monitors are all ready. One of the advantages in CA of having a 2000+ vehicle