PO420 Exhaust Code?
 

Well I was cruising around and my service engine soon light came on. My mechanic has a KAL-Equipment obd-II scanner and the code came up as PO420 (catalyst effeciency below threshold). Any idea's on what it may be. I have FI longtubes with stock nismo exhaust.

This is triggered because the 2nd O2 sensor is detecting is detecting too much oxygen in the stream relative to the upstream O2 sensor. With a catalytic converter this would mean that the catalyst in your converter was used up and you need a new cat to properly scrub the exhaust.

This is a common problem with test pipes, LTH. You can get an Uprev tune and turn the code off permanently or try and come up with a solution to reduce the amount of air getting to the sensor, e.g. extenders, steel wool etc. Or worst case I guess you could try two of these.
O2 Simulator Mini Cat Cel Fix

Exhaust leak where the header meets the exhaust could also cause this as some outside air will sneak in to the mix.

I like ChrisSlicks call on the tune, as long as you have no physical problems (leaks I mean).

The O2 sensor "fool" solutions work well from my experience as long as you don't have an emissions state inspection. In my state, seeing one installed can lead to a failed emissions inspection. Then again, so would the absence of cats.

simplest way that i know works is to tightly roll up steel wool into a ball slightly larger than the size of the bung and shove it into there. i tried shoving steel wool and that didnt work, i tried O2 extenders and that didnt work...but the ball of steel wool worked and has worked for the last 2-3000 miles!

I think I'm doing this trick this weekend.. My SES light just came on again after resetting it once..

Did you use that really fine steel wool ? Not the brillo pad looking stuff, correct ?

i have test pipes on my car and have not seen a check engine light yet. i didn't put them on so idk which brand they are, but are there certain brands or styles that will throw codes and certain ones that wont?

correct. i used fine steel wool and rolled it up tightly into a ball. id suggest doing this with a pair of work gloves on though...i got some nice steel splinters with the first ball i made :shakes head:

In general, the longer the O2 extender is, the less likely it is to throw the fault/light (the O2 has a longer path to travel to the sensor). I don't think it is really brand specific as much as the design/length of the extender that the O2 sensor plugs into. Really, if you are running test pipes or LTH, you should get a tune. As mentioned, UpRev (and Cobb) will allow you to turn this fault off altogether, and you will be able to take full advantage of the increased breathing.

i put z1 test pipes on at work yesterday, drove home and went right back (on my day off) to work and put my cats back on. test pipes sound like poo. i wish i knew that. my fault for not looking further into it. no SES light tho.

i reccomend to get your a/f ratio checked if u dont have some sort of monitoring system already which most of u probably do about 50 miles after test pipes installed. go to nissan and get a tech to drive with you with the cunsult 3 to check your alphas. mine was rich as hell, it may have changed if i kept them on longer. they really did sound awful. i was pissed.

That is odd that you have gotten a CEL with our headers. I can be honest with you and tell you that close to 100 sets sold between the 370Z & G37 and this is only the second or third set that I have seen throw a CEL. Every time before it was always attributed to an exhaust leak or bad O2 sensor. Again, this is not common and I have customers with 10's of thousands of miles on these without a CEL.

If you have time, please call me Monday so we can troubleshoot this together...

Thanks, Tony

Will do Tony. Thanks for chiming in. Holla at ya this week

Does cobb still do stuff for our cars? i heard a rumor somewhere that they stopped doing tunes and such for the z (i could be wrong). Also, if i get a tuner, do i have to get some sort of custom map for test pipes or do some already have test pipe maps loaded?

No, they don't support the VQ35/37 anymore. They have stopped doing support for all N/A applications. Yes, they suck.... With that said, you can still get it tuned and such by a pro-tuner in most cases, but there will be no support from Cobb or future enhancements. The AccessPort should come with a Stage 2 map that is designed for TP or HFC and disables the cat efficiency error code, but a custom tune is always better.

What you see is what you get at this point with the AccessPort. I have a Cobb shop local to me, and they will still tune it for me. I am still going to UpRev as soon as I have a reason to (need for a new tune....), and I would recommend the same for anyone looking for a tune at this point.

I know this thread is a little dated, but were the test pipes installed with an otherwise stock exhaust?
Surprised it would sound like crap just from removing the cats which act like resonators. I'd think with plenty of other resonator/muffler in the exhaust to smooth out the tone, it would only be louder.

My guess is it was the notorious hiss on decel that the VQ is known for when you're running TP's or LTH's. I'm running LTH's and I have to say the hiss is a more pronounced than I thought it would be.