Bad Catalytic Converter?

Hi guys. I have an 01 Taco with supercharged 5VZ-FE. Was running URD 7th injector with piggy-back ECU and 2.2in pulley on the supercharger but just swapped back to 2.37 and removed 7th injector because its smog time. I have a CEL on, ran the code and it came up with P0420: Catalyst System Efficiency Below Threshold Bank 1. I was hoping it was just an O2 sensor so I replaced the sensor before the cat and did the drive cycle and sadly CEL came back on. According to my research there is a few other sensors that could be causing this code but its most likely a bad cat . Would you guys recommend replacing other possible sensors or just replace the cat? Those little sensors are pricy so I don't want to spend all this money if I'm just going to end up buying a new cat in the end.
Also is there any correlation to having a supercharger and cats going bad? The truck only has 120k miles so I feel likes its pretty young to have a bad cat?

 

@eon_blue

 

In my experience the P0420 code means the catalytic converter(s) are bad. Replacing them fixed the code for me after trying just about everything else. The O2 sensors have their own specific codes for when they don't function normally.
The only other likely thing it could be is an exhaust leak before the O2 sensors which would make them think there's an issue with the cats.

Also, I live in LA county and have the 7th injector installed. I've gotten smogged 3 times with it on and never had an issue. I just wrapped the fuel line for it in black electrical tape so it looks like any other vacuum line.

Of course it might depend on the shop but just wanted to throw that out there. Unless they really know what the setup of a supercharged 3.4 is supposed to look like, chances are they're not gonna identify the 7th injector

 

My truck had 60k miles on it when I had to replace the cats. I didn't install the supercharger, the previous owner did. But I suspect he ran it without any fuel mods like the 7th for too long and that did the cats in. I installed Magnaflow CARB approved cats 6 years ago and they've held up great since, no p0420 code and no issues with smog

 

Yeah I was thinking they wouldnt notice the 7th injector but I took it off just to be safe last time thinking I would slap it back on later that day. They ended up failing me for the 2.2inch pulley... Im up in northern California so I guess they take it a bit more seriously here. Unfortunate haha.
So would you recommend doing both cats? Also now that you mention an exhaust leak it is possible I have one because I do have an EGT sensor right after the manifold. But its sealed real good. (well it was 4 years ago haha) may have to look into that. If there is a leak from that though it couldn't be big. Would that be enough to throw a code?

 

It is the rear sensor that reads Converter Efficiency not the front .

 

2001 6cyl had 2 emissions the same year.
Check emissions sticker under hood to insure correct replacement sensors.
Use only authentic DENSO sensors.
https://densoautoparts.com/find-my-part.aspx

 

Go do some YouTubing, there’s ways you can check to see if the cats bad before just throwing money at it.

 

remove the o2 sensor on the engine side(upstream) pour cleaner in the cat. I've used carb cleaner, brake cleaner, seafoam, etc.

let it sit overnight

put air compressor nozzle in the bunghole and blow it out the next day.

run the truck as normal, it will smoke out the exhaust.

after it cools completely, take off both o2 sensors, scrub them off with cleaner and a mild brush.

this takes some time but cost one can of cleaner. usually the cat and sensors are not bad, they are just caked up with exhaust waste.

 

yeah any leak before the rear o2 sensor will mess up its readings. Leak where the sensors are mounted or up near the headers even. Worth looking into.

That sucks they dinged you for the pulley, I'm still only running the stock size one so never had an issue there. I have TRD headers installed and they actually told me that technically the TRD headers are only CARB approved for up to 2003 Tacomas, not 2004s which I thought was weird. Like Toyota just decided not to get the approval for it for that year or something. Luckily they were cool about it though and didn't fail me for it.

of course I only take it to that shop now, if I had to remove the headers for smog that would be a huge pain.

 

How bad is your rotten egg smell from your muffler? Did it get stronger over time?

 

That sulphur smell is very disguised when the cats gone bad

 

I have a friend with the SC & TRD headers, and whoever originally manufactured the headers mis-stamped the CARB info on them or something like that, and they failed him. He had to get like notarized certs and jump through a million hoops just to be able to get it through. He considered just selling the truck to someone out of state for awhile, but came to his senses and didn't let the truck go, haha

 

Is his an 04 as well? If it is then I wonder if that's the same issue I ran into. Because it literally makes no sense why it wouldn't be good for the 2004s considering they're the same truck as the 2003s....but yeah I got lucky with my shop. He basically told me he thinks it must be some kind of mistake and he'd let it slide.

 

02. It was a physical defect on a stamp if I recall. Been a few years.

 

Got the part from Toyota pasts dealer. They checked my VIN so I know it is the correct part. The code its throwing says bank 1 so toyota parts told me to replace sensor before the cat.

 

Yeah I might look into TRD headers. I have an 01 so shouldnt be an issue there. But yeah ive seen pics of the headers and it looks like those things barely fit haha. Removing them would be a pain

 

good luck finding a set of TRD headers haha, they were discontinued years ago and next to impossible to find these days, unless they are takeoffs...I see them occasionally in the for sale section on here but they go quick

 

How would I go about testing for a leak before Sensors?

 

Trust me, the parts guys don't know what they're talking about. Bank 1 just means drivers side manifold, bank 2 is passenger side. With only the "bank" information you do not know which sensor it could be referring to, only which side. If you're truck is post 2000.5 then you have front AFR sensors, which aren't O2 sensors, the sensor(s) AFTER the cats are O2 sensors. Post-cat sensors fail all the time which will throw a P0420 code as well.