P0420...what do I do?

[babiebluboi]

I've done some research on the forums and no one has actually come up with a solid answer. My car threw a CEL code P0420 (Catalyst System Efficiency Below Threshold). I believe that has something to do with the cat and maybe the O2 sensor. The O2 sensor that plugs into the turbo manifold is about a year old.

The problem is that I have a downpipe-back straight pipe exhaust, not a high-flow cat. This means that I don't have anywhere to put my second O2 sensor, so it's just dangling under the car. I've had this set up for a couple years already w/o any problems, but this CEL P0420 code just popped up yesterday. The car seems to run fine, but there's white smoke coming outta the exhaust and it doesn't smell normal.

What should I do? Some people suggested getting an O2 sensor bung and weld it onto the exhaust system somewhere. Other people said that I should get an O2 simulator. What do you guys think?

 

[jake247]

I hear simulator's work well... not that I use one... etc. etc. no cel though


I've heard of using two bungs so that the sensor does not fully stuck in the exhaust works as well. I don't know if that works... that's not the way I went.


There's always dsm link too.

Or you could build your own resistors so that it sees the value that it's supposed to, if you're good at that kind of thing.

 

[babiebluboi]

I hear simulator's work well... not that I use one... etc. etc. no cel though


I've heard of using two bungs so that the sensor does not fully stuck in the exhaust works as well. I don't know if that works... that's not the way I went.


There's always dsm link too.

Or you could build your own resistors so that it sees the value that it's supposed to, if you're good at that kind of thing.

DSMlink is too pricey. I'm glad you mentioned the resistors. I actually bought an "O2 simulator" off eBay and was wondering why I got 2 wires (one black, one gray) with resistors in between wrapped with heat shrink. What exactly does that do? It came with directions that doesn't seem too difficult, but it still requires me to plug the O2 sensor back, which I don't have anywhere to plug it.

 

[jake247]

there are two circuits in the o2 sensor.

one is for the heater coil (2 wires), because it has got to be hot to work.

the second is the sensor part (other 2 wires). the resistors would be for the sensor. because electrical blah blah magobble isn't my thing, basically X amount of electricity comes into resistor, and resistor 'resists' and only 1/3 X amount of electricity comes out. Or whatever the resistor is rated for.




SO you're going to want a bung or something to screw the o2 sensor in because it gets hot (trust me, i tried to wrap it in aluminum foil and leave it under the driver seat.) and you'll want to put the resistors in line. And because the thing you got is in heat shrink, i would recommend having that inside of the car so it's not affected by water from a rainy day or something so it doesn't short.

You could use more resistors or farad's or I don't know what they are, there are directions on vfaq.com. The heater circuit left unplugged will also throw a different code.

 

[babiebluboi]

I talked to the guy at the exhaust shop and he said that he'll help me out with a O2 simulator. While I'm at it, I'm going to do a custom downpipe and the whole exhaust system. When I get the O2 simulator in, I'll let you guys know how it runs.

 

[XilArAtiNG]

with the o2 simulator is a good way to get rid of the basically useless cat o2 sensor.

Another way is if you know a buddy with a way to hook up to the car you can have them manually turn off the I/M Readiness test for the 2nd O2 sensor and that way you dont need the resistor and your car passes emissions with flying colors...unless they use a probe test in your state that is..

 

[onekillerdsm]

hey guys i have a quick question.... on this cod p0420 its stating that catalyst system efficiency bellow threshold (bank 1) does the bank 1 mean that it is detecting sensor 1 as being bad???? or sensor 2????

 

[95TalonOwner]

hey guys i have a quick question.... on this cod p0420 its stating that catalyst system efficiency bellow threshold (bank 1) does the bank 1 mean that it is detecting sensor 1 as being bad???? or sensor 2????

Bank 1 is the side of the engine that cyl 1 is on, since it's a 4 cylinder, bank is basically irrelevant. P0420 means you need a new converter or you're just driving without one.

 

[twoTSis]

Bank 1 is the side of the engine that cyl 1 is on, since it's a 4 cylinder, bank is basically irrelevant. P0420 means you need a new converter or you're just driving without one.

Does it have any negative affects? Other then the annoying fact that my check engine light is on? My car is stock except for NGK plugs and 10.2 wires, I'm guessing something is shot.

 

[95TalonOwner]

Your cat is shot. Could have negative effects if it is clogged.

 

[twoTSis]

Well I was planning on going with an Apexi N1, I guess here's some motivation. I was told to try resetting it to see if it comes back on. You think I should try that first?