This for sure. Unburnt air/fuel is read by upstream O2 sensor as lean condition and extra fuel is injected. At the same time, unburnt air and fuel are hitting the cat and overheating it. Long periods running rich (well, catalyzing rich exhaust) ruins cats.

-Charlie

Going through this now! I'm still confused. Lol!! The previous owner had a new cat installed prior to my purchasing, passed Smog and sell went through, no issues. First time I had to have it smogged, all went well. Last year I failed for missing one cat, and for the one I have on, being the wrong one for my engine family???? Another thing that pisses me off is how they label it on the Smog test results. They label it as "tampered", which sounds malicious. Anyways, im trying to locate the correct part numbers so I can get this handled. By chance can anyone provide me the part numbers and approximate cost? Aftermarket preferred of course. I've searched but cannot locate them. Am I supposed to have two cats? Are they sold separately or are they sold together? Has anyone successfully had the dame problem corrected? This has been a nightmare. This truck is going to be my son's for college and I want to always hold onto it. I love it and just want to get this put behind me. If anyone can help, I would truly appreciate it. Thank you all for your help, and the information on this site. Always very helpful folks on here and just knowing that help can be found and shared with each other is fantastic. It's truly a brotherhood type of feel here and I sincerely appreciate the information. Take care all and I pray to hopefully hear from any and all that can aid me.

Pop open your hood and look at the smog sticker that is stuck on the underside of the hood itself. It should look like this:



In the top left hand corner, this sticker says "SFI, A/F S, TWC(2) HO2S". Can you post what yours says? That way we will know what kind of emissions your 4Runner has and needs. Also please let us know if the sticker makes ANY mention of California like this one does.

That's the ticket, but keep in mind that a PO might have swapped hoods. Mine has a sticker that says TRD Supercharger, but alas, the hood has something the engine does not. 2 cats for CA is what you need if the Newark in your profile is East Bay and not NJ.

Magnaflow sells replacements. 3 grades Depending on model.

There’s 2 California grades. The “original” OEM level, and the newer standard LEV if I remember right. I have a set in the garage of the OE magnaflow Cali converters. I just need to get them in one of these days.

Their website is good for showing what’s needed.

Yep. Previous owner ruined my set. They thought spark plugs were lifetime parts apparently.

Thank you. I will get the tag uploaded. I appreciate all responses!!!!

Sorry, upload keeps failing. This is what it says, and yes it mentions California.

Engine family: XTYXT03.4DBP
Evap Family: XTYXE0095AE0

THIS VEHICLE CONFORMS TO U.S. EPA NLEV REGS. APPLICABLE TO GAS FUELED 1999 MODEL YEAR NEW TLEV LIGHT DUTY TRUCKS & TO CALIFORNIA REGS. APPLICABLE TO 1999 MODEL YEAR NEW TLEV LIGHT DUTY TRUCKS.

CATALYST
OBD II CERTIFIED

Ok, so you have a 1999 with California emissions. My voodoo 4Runner smog skills are a bit weak today and I can't recall the specific smog setup on a 99. Can you also type of the phrase I mentioned above? It should say something like "SFI, A/F S, TWC(2) HO2S".

I believe that you do have a version that need to have two catalytic converters but, like others said, you don't live in California. Where this gets real weird is I don't know if your state allows for an emissions modification in taking a CA specific smog rule and reducing that down to one catalytic converter. These cats are not cheap, even a Magnaflow converter is $500+ (which I recommened, I also have one on mine). I would call another smog shop and get another opinion. The fact that one shop passed it with one cat and the next failed it means it may be a little known rule or subjective decision.

In my smog experiences here in CA, there's smog guys who spend all their spare time reading regulations and know everything down to the punctuation. Then there's smog shops that just make sure it's 'good enough'. I suggest finding a shop that thinks one cat is 'good enough'. I have one of those around here that passes my very smog illegal 4Runner every two years.

Sorry, I'm an idiot.

SFI, HO2S(2), TWC

And actually i do live in California. I'm in Sacramento. My mistake for not being clear. Sorry for causing all of the trouble by having you reiterate needed information. I appreciate your help and patience.

And yes, I know what you mean relative to some shops knowing every piece of info and detail. It passed the emissions step twice, even at the Smog Referee. The Smog Referee called his supervisor J. Baltazar, nice name drop, to ask for an exception, but no, he would not allow it. I had thought that was the purpose of the Smog Referee? Emissions is allegedly the vital piece but, California loves screwing the little guys so, I was not shocked, disgusted, but not shocked.

I have a federal emissions truck that was brought in from out of state, smogged and registered successfully in CA. Then I swapped hoods with my CA emissions vehicle... can't wait for the fun to begin on my next smog check.

MagnaFlow makes a federal emissions Cat that is legal for sale and use in CA, with all the correct registrations with CARB, etc

MagnaFlow Universal Catalytic Converter California Grade CARB Compliant 334006 - Stainless Steel 2.5in Inlet/Outlet Diameter, 16in Overall Length, No O2 Sensor - CA Legal Replacement https://a.co/d/bnCqGYZ

I don't need it yet, no emissions codes have been thrown, but at that price I'd like to have it on the shelf.

Now to figure out the best course of action for the hood sticker connundrum...

Sent from my Pixel 4 XL using Tapatalk

That text hints at non-CA spec vehicle. Very confusing.

in '99, the CA spec was an AF sensor, O2 sensor and two cats (TWC)
in '99, the Fed spec was 2 O2 sensors and one cat (TWC)

Does the exhaust look modified?

-Charlie

Yeah I'm thoroughly confused too. That code means this:

SFI = Sequential Fuel Injection
HO2S (2) = Oxygen (O2) sensors, two (2)
TWC = Three way converter, just one

I looked up your engine family code XTYXT03.4DBP and the California Air Resource Board thinks you have a 1999 Toyota Tacoma. Is that correct?

XTYXT03.4DBP Test Group / Engine Family Toyota Emissions

The 4Runner and Tacoma share a lot of things but they have differences as well. It may be that the 1999 Tacoma doesn't have a 2 catalytic converter version. Also I live in Citrus Heights, like 15 minutes away from you ha.

90% correct
That engine family code is for a federal emissions vehicle, yes.

My 4WD 4runner with federal emissions has the same codes except the engine family code ends with the same 4DBP, same as the @rrodness1970

Here's my sticker for reference

@rrodness1970 can you just post a pic of your hood sticker and validate, visually how many cats you have?

EDIT: just reread, understand now.

You need the sticker that came with the cat the PO installed that has the EO# for the installed equipment so the tech can validate what was installed.

Without that, and it's a good thing you are in Sacto, you will have to make an appt with a DMV smog referee, located in Sacramento, and get a review and an exception, and have it documented on the CA registration database under your trucks VIN that your installed equipment conforms with the original equipment of the vehicle - which they can validate using the VIN.

It's a PITA