Exhaust system question

[99yota4]

I've been getting the CEL P0420 pretty regularly now and it is bothering me. I am 80% sure that it is the Catalytic converter because it takes good O2 sensors for the P0420 code to be thrown. (research done on 4x4wire.com) Here's the link to the information I gathered.

4x4Wire's TrailTalk Forums: Trouble Code P0420

I've been told I have TWO Catalytic converters but I am not sure. I would go under the truck and look at it myself but I have had no time to get out and work on the runner. How can I find out what I have under there. Also, if it is in fact the cats that need to be replaced, should I replace the entire exhaust system as well? I was looking to get a magnaflow muffler anyway. If so, where do you guys recommend getting it from. Thanks in advance!

I forgot to mention that it seems like the CEL with the same code (P0420) kept coming on when there was moisture (Rainy weather, rainy roads etc)
I also noticed that the CEL goes on alot more since my friend borrow the runner and filled her up. I usually gas with Shell, but I need to find out what she put in it, I dont know if that will effect the frequency of the CEL coming on!

 

[Stick Figure]

Mine throws the same code after driving at slow speeds for long periods. Usually any type of offroad, or HEAVY traffic. Basically anytime the cat can cool down. I know its the cat because of the numbers from the recent smog test. As far as how many cats you have, just depends on if you have a CA emissions, or federal vehicle. You could call Toyota w/ the VIN number, but its easier to take a look under it.

 

[t4r4life]

I've been getting the CEL P0420 pretty regularly now and it is bothering me. I am 80% sure that it is the Catalytic converter because it takes good O2 sensors for the P0420 code to be thrown. (research done on 4x4wire.com) Here's the link to the information I gathered.

4x4Wire's TrailTalk Forums: Trouble Code P0420

I've been told I have TWO Catalytic converters but I am not sure. I would go under the truck and look at it myself but I have had no time to get out and work on the runner. How can I find out what I have under there. Also, if it is in fact the cats that need to be replaced, should I replace the entire exhaust system as well? I was looking to get a magnaflow muffler anyway. If so, where do you guys recommend getting it from. Thanks in advance!

I forgot to mention that it seems like the CEL with the same code (P0420) kept coming on when there was moisture (Rainy weather, rainy roads etc)
I also noticed that the CEL goes on alot more since my friend borrow the runner and filled her up. I usually gas with Shell, but I need to find out what she put in it, I dont know if that will effect the frequency of the CEL coming on!

yes third gen 4runner has a pre cat and a after cat, there is a 02 sensor after the muffle, and im pretty sure there is one 02 sensor in between the pre cat and the after cat,its easier to just replace the whole exhaust, go check with toyota dealer to see where are the 02 sensor is located if one sensor is before the two cats, it'll just be easier to replace the whole exhaust system.

 

[99yota4]

Now when you say replace the whole exhaust system, do you mean with an aftermarket type system? If so where can I get one and which is the recommended system for a little added performace? Thanks

 

[t4r4life]

Now when you say replace the whole exhaust system, do you mean with an aftermarket type system? If so where can I get one and which is the recommended system for a little added performace? Thanks

actually i dont like either flowmaster or megnaflow both are way overrated and over priced(even tho i have a flowmaster but i got it for free:biggrin2, if you dont have to smog you can just get a urd 02 senor simulator which can eliminate having cats at all and just run straight pipe from headers to the muffler, that way you just have to buy the muffler and use the existing pipe.

 

[99yota4]

What other options do I have for replacing the exhaust system? I don't want to just replace the Cat without figuring out why it's causing the cat to fail. I know cats are designed to last the life of the vehicle so there has to be something wrong. Thanks!

 

[99yota4]

Hey guys, so I still have the same problem with the P0420 code. Today I was seafoaming my runner and used the brake boost hose to suck the seafoam into the intake manifold. When I was reving the engine using the lines at the throttle body, I noticed smoke coming from under the engine. I noticed I have a small exhaust leak! It's coming from the pipe that connects from the headers to the pipe below. I will try and fix that gasket and hopefully the exhaust leak is fixed.

I was wondering if THAT could cause a P0420 code?! I'll post again when I get that gasket swapped out and see if the CEL comes on after that.