Recurring PO420

[ameining]

So I have done the search thing, and can't seem to pinpoint what it is I think is happening. I throw a PO420 when I make long drives......sometimes. It has probably happened a total of 5 times in the last 8 months. I have only cleared the code twice, the remaining times it will clear itself...?

I am under the impression that it may be the downstream MAF...but I do not know where that part is. I changed the MAF on the intake before, that was a piece of cake. My truck has the dual cat's, so are there actually 2 downstream MAF's? Does anybody even think that this is the problem??

 

[Stick Figure]

P0420 is the catalytic efficiency code. Basically it means your rear o2 sensor is saying that your cat isn't doing its job. If you don't have any exhaust leaks, then you just need to determine if its a sensor problem or actually the catalyst themselves.

http://www.ncttora.com/fsm/1996/SIL...2rmsour/2002/024runne/di/eg5vzfe/cip0420o.pdf

There is the factory troubleshooting process.

 

[spitvenom]

yup, bad catalytic converter, after cat 02 or exhaust leak, hit your cat with your fist, if it rattles its for sure the cat!

 

[GlobemasterMIII]

Bought my 2005 4Runner a few months ago & it was throwing the catalyst efficiency code. The previous owner took it to a shop & they quoted him somewhere around $1000-1500 (maybe more) to replace the Cats...I wasn't too concerned about it & I paid like $2K under blue-book because of the Check Engine Light being on. I decided to replace both post-Cat O2 sensors (~$90 each), thanks to the advice on this forum, and the CEL hasn't been back for over 2K miles. Moral of the story: before you go drop hundreds-to-thousands of dollars for new Cats, spend $190 & 30min to change out your O2 sensors. Good Luck.

 

[T4R_Finally]

The downstream o2 sensor is the one that throws that code. First check for any exhaust leaks upstream of that sensor. If there are none, replace the sensor (dont buy Bosch), reset the cel and drive and see if you get the code again. If you do, the issue is most likely a bad cat system. For me, replacing the sensor did the trick. Bought a denso sensor online for $62 shipped and changed it myself.

 

[spitvenom]

Glovemaster on your 05 it would have been highly unlikely to be the cats because its newere and lower milage, something would have to be reallllllly wrong to either run reallllly hot or reallly rich/dirty to clog the cats, on 3rd gens with higher mileage 150k+ its possible to be the cat (1) but you dont have to buy the dealer one for 1k-3k you can get a legal compliant one for 220-350 from exhaust shops for one.

Yes check for leaks, if no leaks are present, tap cat and if it rattles its for sure bad so replace, no rattles, change after cat o2 sensor first then dont forgot you need to manually with a scanner reset the check engine light.
:banana:

 

[ameining]

Part numbers??

I have the CA version with 2 cat's...and I have yet to see a writeup on the location of these sensors.

Anybody have part numbers/photos to show the location of the specific sensor that may be bad? ? ? ?

Thanks!!!!

 

[snow junky]

its on your exhaust. make sure your car is cold before touching the cat.




you can check to see if your o2 sensor is working if you have a code reader that will show you real time data.......if theres only one sensor behind cat the V will be alot more stable then your upstream one. my guess is that your cat is going bad


its going on when your on long trips because it is doing a run cycle test....

if you want a cheap fix install a spark plug no fouler $7.00

 

[bitchaaz]

Which spark plug no foul do you get. Is there a specific size or length or #?

 

[mikebontoft]

damn it I had a whole big thing typed up earlier and I see it didn't even post.

I was saying the non foulers are straight up a way around fixing the problem. I'm not sure how big the thing has to be, I don't remember. I believe you have to drill the opening out some. what it does is move the 02 out of the direct stream of exhaust and its supposed to "read cleaner" that way.

but that reminds me if what I was going to say. the non fouler would be an excellent diagnosis tool. install it, clear the codes, go for a drive cycle and see if you still get the code or not. if you do, the sensor is the problem.