[Slimee]

I've been procrastinating this post for the better part of 2 years now, and have searched the forums and google for more hours than I've been able to track over the past 3 years. So back in 2016 I pulled a P0420 code, and received so much mixed information it made my head spin. Do nothing, replace rear cat, replace both cats in Bank 1, replace O2 sensors, etc etc. I partially regret the decision I made next, which was after talking with my Toyota tech (a friend who works at a Toyota Dealership who often does work on the side for me), and I went ahead and ordered an aftermarket set for Bank 1 (MagnaFlow, both the exhaust manifold and the rear cat). But I didn't get it installed right away, mostly because after coming back East from the roadtrip I was on in Colorado and Utah that I went thousands of miles before pulling the code again. Maybe it was a fluke I thought (after pissing away almost $700 on the new set). Everytime I drive out west I pull the code, and when I wipe the code out there I frequently pull it over and over... sometimes I go a thousand miles, sometimes two thousand, sometimes two hundred. I've started having doubts that it's soley the cat, if even the cat at all, and maybe it is just O2 sensors (part of me hopes I'm wrong because I can't return $700 in parts I ordered back in 2016)

The question is, am I foolish for proceeding with replacing the cats? Should I be replacing sensors too while I'm at it, or not waste anymore money until I'm sure?

My most recent roadtrip this past summer I pulled the code 3 times, and once after getting back home...although it's ironically now been at least a thousand or more miles since the last time I've pulled the code too.

I've got a 2003 V6....which also means everytime I pull the code my entire traction control system shuts off because of that stupid zero point calibration thing.... so I can never just clear the code, I always end up having to disconnect the battery and reset EVERYTHING so I can get my ATRAC back.

[ac1617]

https://www.amazon.com/JGR-Universal...8-4&th=1&psc=1

Buy these and get a muffler shop to install them on the downstream O2 sensors for you (shouldn't cost anymore than 0.5 hours labour). Countless individuals use these with success.

[RonJR]

O2 sensors have a limited life. Catalytic converters will last indefinitely unless abused by a poorly running engine. Translation: Do the cheap, easy, and likely thing first and replace the O2 sensors. For about $200 and an hour of your time per bank you could have had this done 2 years ago and probably saved yourself hours of fussing with the codes. Your engine needs a working front air fuel sensor to run right, and the rear O2 sensor ensures the cat is working properly to control emissions.

BTW, you do not have to pull the battery to redo the zero point cal for the VSC. Here's how to do the zero point cal in just a few minutes.

[Slimee]

Originally Posted by RonJR

O2 sensors have a limited life. Catalytic converters will last indefinitely unless abused by a poorly running engine. Translation: Do the cheap, easy, and likely thing first and replace the O2 sensors. For about $200 and an hour of your time per bank you could have had this done 2 years ago and probably saved yourself hours of fussing with the codes. Your engine needs a working front air fuel sensor to run right, and the rear O2 sensor ensures the cat is working properly to control emissions.

BTW, you do not have to pull the battery to redo the zero point cal for the VSC. Here's how to do the zero point cal in just a few minutes.

Hindsight's 20/20. Had 3 separate places tell me the same thing, bought the cats, and then they just sat in my house collecting dust while I delayed having them installed. About a year after buying the cats I realized I'd likely need to replace the O2 sensors anyway, and that I probably should have started with them first and seen if I pulled the codes again.

[hinmo24t]

im more of a dog person

[rodsrunner]

The fix from years ago https://www.toyota-4runner.org/problems-and-warranty-issues/92619-10$-fix-failed-catalytic-converter.html

[techno]

For starters, whoever told you to replace the rear cat or both cats in bank one, is a moron. The rear cats are not monitored by any sensors and can never trigger any codes. They exist only for cleaning up emissions during the warm up cycle for states that do or used to do tail pipe checks during state inspection procedures.

There's a clearly defined procedure for troubleshooting these codes, and I don't mean to sound rude, but to go ahead with the least likely and also most expensive fix as the first option without doing any testing is kinda insane. It's a shame three places told you this.

It's highly likely that the code 'disappeared' for periods of time because the exact driving/engine conditions that are needed to trigger the CEL were not met. Specifically, the requirements that a complete driving cycle is done, the condition lasts for 30 secs or more, and that 2 complete driving cycles are done. There's a good chance the code sat in pending waiting for it to occur a second time, which it never did because the driving cycle was not completed (for example: you did a short trip that didn't warm up enough or get higher than 4th gear).
If you haven't read this procedure yet, it might help you understand it a bit more. http://4runnerclub.com/i/4r_files/fs...rr/0050034.pdf

[duffdog]

I have an actual solution for this that passes CA smog and does not set off any codes and is not visible during smog checks and doesn't even require a catalytic converter to be installed. PM me for details.

[Slimee]

Originally Posted by techno

For starters, whoever told you to replace the rear cat or both cats in bank one, is a moron. The rear cats are not monitored by any sensors and can never trigger any codes. They exist only for cleaning up emissions during the warm up cycle for states that do or used to do tail pipe checks during state inspection procedures.

There's a clearly defined procedure for troubleshooting these codes, and I don't mean to sound rude, but to go ahead with the least likely and also most expensive fix as the first option without doing any testing is kinda insane. It's a shame three places told you this.

It's highly likely that the code 'disappeared' for periods of time because the exact driving/engine conditions that are needed to trigger the CEL were not met. Specifically, the requirements that a complete driving cycle is done, the condition lasts for 30 secs or more, and that 2 complete driving cycles are done. There's a good chance the code sat in pending waiting for it to occur a second time, which it never did because the driving cycle was not completed (for example: you did a short trip that didn't warm up enough or get higher than 4th gear).
If you haven't read this procedure yet, it might help you understand it a bit more. http://4runnerclub.com/i/4r_files/fs...rr/0050034.pdf

I agree, if I could go back in time I'd smack myself and stop myself from buying them, but I'd been so convinced by that point that that was absolutely what it was, so I bought them... then between then and now I slowly started realizing that was a mistake, which really only furthered the procrastination. I have the Sensor 1 and 2 from Denso on their way, gonna go ahead and put them in and just monitor things.

Can't say I'm looking forward to trying to sell the manifold and rear cat if it turns out to be just O2 sensors... There's definitely a small part of me that's hoping that my cats do turn out bad just so I didn't waste the money (which it's looking more and more like I did)

Life Lessons are rarely learned the easy way.

[2003-4x4runner]

Originally Posted by Slimee

I've been procrastinating this post for the better part of 2 years now, and have searched the forums and google for more hours than I've been able to track over the past 3 years. So back in 2016 I pulled a P0420 code, and received so much mixed information it made my head spin. Do nothing, replace rear cat, replace both cats in Bank 1, replace O2 sensors, etc etc. I partially regret the decision I made next, which was after talking with my Toyota tech (a friend who works at a Toyota Dealership who often does work on the side for me), and I went ahead and ordered an aftermarket set for Bank 1 (MagnaFlow, both the exhaust manifold and the rear cat). But I didn't get it installed right away, mostly because after coming back East from the roadtrip I was on in Colorado and Utah that I went thousands of miles before pulling the code again. Maybe it was a fluke I thought (after pissing away almost $700 on the new set). Everytime I drive out west I pull the code, and when I wipe the code out there I frequently pull it over and over... sometimes I go a thousand miles, sometimes two thousand, sometimes two hundred. I've started having doubts that it's soley the cat, if even the cat at all, and maybe it is just O2 sensors (part of me hopes I'm wrong because I can't return $700 in parts I ordered back in 2016)

The question is, am I foolish for proceeding with replacing the cats? Should I be replacing sensors too while I'm at it, or not waste anymore money until I'm sure?

My most recent roadtrip this past summer I pulled the code 3 times, and once after getting back home...although it's ironically now been at least a thousand or more miles since the last time I've pulled the code too.

I've got a 2003 V6....which also means everytime I pull the code my entire traction control system shuts off because of that stupid zero point calibration thing.... so I can never just clear the code, I always end up having to disconnect the battery and reset EVERYTHING so I can get my ATRAC back.

I also had the PO420 code and I just replaced all the O2 sensors and it fixed the issue. I have over 235k miles and so far so good. Start with the sensor and go from their.

Also, not sure why your doing a zerpoint calibration afterwards. You should only do a ZPC if the traction/stability control lights wont go off after resetting the codes or disconnecting the battery. Good luck.