Dreaded P0420 code

Had the same problem randomly for 3 years. Messed my cat up and replaced it with a magna flow. Haven't had the code since then

 

I replaced rear o2 sensor and it fixed my p0420

 

I've been dealing with this error code on my 2000 prerunner 3.4L for over 3/4 yrs now. Some times it goes off by its self. I can't tell any difference in performance if the CEL is on or off. I only worry about it once a year, my State/county does inspect emissions. I've discovered I can clear it with my ODB gadget (best $12 I ever spent) and Torque app, drive approx 200 miles and I can pass inspection, it will usually come back at around 500 miles. My cat was stolen in 2007, and I couldn't afford an OEM, so I bought a magna-flow, but it had to be welded in, and my flanges cut off. At the time it saved me over $600, and seemed worth it. The O2 sensors were spared, and are original ones from the factory. I haven't tried one of those, and probably won't until I can't get it inspected. I agree with Mr. Biscuits, clear it, see if it comes back, try the easy/cheap fixes, and if you don't have to worry about emissions for inspection, don't worry about it unless you can tell definite performance/operational issues related to it.

 

Go check out URD. If you don't need to worry about emissions....
Underdog racing development- their product fixed my 420 issues

 

Guess it was just a hiccup cause it hasn't come back on after I cleared it

 

Ok. I got that code coming home from school today.

This past weekend my truck went in for a much overdue tune up and they replaced the O2 sensor Idk if it was front or rear, and cleaned off my dirt-encrusted MAF sensor which had been throwing a P0171 code for months. I reset that code and it hasn't come back but now this one has come up. I also replaced my spark plugs and a vacuum hose.
It pretty much sounds like I've screwed with everything that could cause this code very recently. What should I do?

Also, what does this code means in terms of safety to drive and will it hurt my taco?



It's a 2001 TRD with a K&N air filter if that helps

 

It won't hurt the truck. It just means that the catalytic converter is working at below 95% efficiencyou, which means that you're polluting a little more lol. I would say just erase it and see if it pops up again. That's what I did for mine. Hasn't come back yet

 

Awesome. As long as it doesn't hurt my truck I'm cool with it.

 

I recently had the same issue with my '99 4-banger. I've read through several previous posts on the subject. From what I've gathered, the code could mean an issue with:

• one of the sensors
• the cat
• an exhaust leak
• poor quality fuel

One post mentioned using a specific fuel additive which is supposed to clean the cat. I couldn't find it at my local auto parts store so I tried this stuff called Guaranteed To Pass. It says it cleans the who fuel system and emissions-related equipment. Within 50 miles, my CEL turned off. Who knows how long it'll last, but for $12 I think it's a great place to start.