What could be next P0420

[Thatgoodfellow]

I’ve had the P0420 code for catalyst efficiency since I bought this vehicle. I’ve changed out the big culprits I have found searching on these forums which include mass airflow sensor, both upstream and downstream O2 sensors and I cleaned the throttle body but still no luck.

I was just gonna forget about it and live with it but a couple months ago after changing my valve cover gaskets I noticed the code went off and stayed off for about 3000 miles. Until recently, after noticing my oil was a little low from my last oil change I went ahead and topped it off and then boom all the sudden the code came back.

Completely lost so just looking for answers. I know it’s a kind of a shot in the dark with this code, but the only thing I can think is that my engine is burning oil and somehow that’s during the code.

Thanks guys.

 

[Endlessblockades]

How long does it take to return if you clear the code?

 

[Thatgoodfellow]

How long does it take to return if you clear the code?

It has been either immediately or within a day or 2 up until this last time where I went about 3k miles.

 

[Endlessblockades]

It has been either immediately or within a day or 2 up until this last time where I went about 3k miles.

Is your exhaust system downstream from the cat tight and not rusting through anywhere?

 

[mtbtim]

I've dealt with this code for around 10+ years. The only parts I have replaced is the upstream and downstream O2 sensors.

If you're due for your registration and you need to get a smog certificate, it's worth trying a product like Cataclean. Follow the instructions and drive it for a while. If your catalytic converter was clogged, you'd know because your engine performance would be very poor.

 

[Thatgoodfellow]

I've dealt with this code for around 10+ years. The only parts I have replaced is the upstream and downstream O2 sensors.

If you're due for your registration and you need to get a smog certificate, it's worth trying a product like Cataclean. Follow the instructions and drive it for a while. If your catalytic converter was clogged, you'd know because your engine performance would be very poor.

Fortunately, I live in Kansas and don’t have to worry about that and I don’t notice any performance issues. I’ve about come to terms with just living with the code on.

Is your exhaust system downstream from the cat tight and not rusting through anywhere?

Not from what I could tell, but I have considered taking it to an exhaust shop to see what they think. That might be the next to last thing I could try.

 

[mtbtim]

Fortunately, I live in Kansas and don’t have to worry about that and I don’t notice any performance issues. I’ve about come to terms with just living with the code on.

If you don't need to smog your rig, I wouldn't worry about it.

 

[Endlessblockades]

Fortunately, I live in Kansas and don’t have to worry about that and I don’t notice any performance issues. I’ve about come to terms with just living with the code on.



Not from what I could tell, but I have considered taking it to an exhaust shop to see what they think. That might be the next to last thing I could try.

The code isn't going to hurt your vehicle, but any CEL annoys me a bit. I get the 420 every couple of years and I tighten the exhaust flange bolts (no rust) and the connector bands (aftermarket Magnaflow cat-back exhaust) and it disappears. The final sensor is pretty perceptive and will throw the code if you have leaks in my experience. I've posted about this a few times and sound like a broken record but it can be a low-cost fix worth trying.

 

[Devbot]

If I'm not wrong, on our vehicles p0420 trips when efficiency reaches like 95% or something, so it's really not much to worry about. If the light just annoys you and Cataclean doesn't work out, you could also try spraying the cats with brakleen through the O2 ports and a straw nozzle. Usually that washes off a bunch of crap that's making them dirty. If you use Cataclean try and drive it like you stole it so the increased exhaust temps help burn off whatevers on the honeycomb

 

[Twisted Sid]

Look into a O2 sensor spacer.
I know of a 4runner has one that it has passed its last few smog tests and the spacer was used to "fix" a reoccurring p0420 code

 

[Robb235]

When I installed the turbo, it eliminated both of my cats. I used a spacer that has the Toyota 2-bolt flange, and it has eliminated my P0420 code. Only place I’ve found this particular spacer is on Ali Express. Since its sole purpose is to fool emissions checks on the vehicle, I don’t think it’s allowed on eBay or Amazon. Just search for Toyota Oxygen Sensor Adapter on Ali Express, took about 2 weeks to get here from China.

 

[Thatgoodfellow]

When I installed the turbo, it eliminated both of my cats. I used a spacer that has the Toyota 2-bolt flange, and it has eliminated my P0420 code. Only place I’ve found this particular spacer is on Ali Express. Since its sole purpose is to fool emissions checks on the vehicle, I don’t think it’s allowed on eBay or Amazon. Just search for Toyota Oxygen Sensor Adapter on Ali Express, took about 2 weeks to get here from China.


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Thank you for that, I have actually been looking for something to cheat the 02 sensor but I couldn’t find anything. I’ve also been curious about eliminating my cats completely as well. I’ve read mixed reviews on removing them. But you have been happy so far without the cats? No issues you’ve noticed from eliminating them?

 

[Robb235]

Thank you for that, I have actually been looking for something to cheat the 02 sensor but I couldn’t find anything. I’ve also been curious about eliminating my cats completely as well. I’ve read mixed reviews on removing them. But you have been happy so far without the cats? No issues you’ve noticed from eliminating them?

I've not had any adverse issues. I also eliminated because the downpipe and midpipe that came with the CX Racing turbo kit didn't mate up to the California-style emissions, 2 catalytic converter setup I had from the factory. So I just replaced from mid pipe to the muffler inlet, and have a flex pipe instead of a catalytic converter.

 

[Robb235]

I've dealt with this code for around 10+ years. The only parts I have replaced is the upstream and downstream O2 sensors.

You should do a Toyota Time video showing installing this sensor spacer and your results lol. It's permanently killed the P0420 code for me. Unless YouTube objects to videos showing circumventing emissions controls?

 

[Thatgoodfellow]

I've not had any adverse issues. I also eliminated because the downpipe and midpipe that came with the CX Racing turbo kit didn't mate up to the California-style emissions, 2 catalytic converter setup I had from the factory. So I just replaced from mid pipe to the muffler inlet, and have a flex pipe instead of a catalytic converter.

Awesome that’s good to hear. I have the same California emissions on mine. I may have to hack off those cats down the road and put a straight pipe to the muffler.