Anyone know where I can find out what codes are what? I am throwing a PO420 and want to know what it is.

 

Call you local dealer and tell them the code and they should be abel to tell you if they are cool about things.

 

PO420 = catalyst efficiency below threshold bank 1.
Usually bad Cat or bad o2 sensor.
I would say bad 02 on this new of a car. Cat should be good for a long time.

 

Ok so is this check engine light hurting me? Am I doing any daage and if I just replace the O2 sensor, will the check engine light turn off? How do I know which of the two is bad?

 

if the light just turned on you shouldnt be that bad yet. you could replace it if youd like but it gets a bit pricey. If by O2 sensor you mean the MAF then you may just have to clean it. you can go to autozone and pick a MAF cleaner and just follow the directions.

 

Well this turned on ever since I put y header on which was about to weeks ago. Since then I have also put on an S-pipe. The car only has 21K on it and I can't see how the O2 sensor would have already gone. I know that putting a header on will throw a CEL and I a not sure if that i all it is. I really don't think it is the MAP sensor cause that wouldn't really make any sense, but I also don't want to spend the cash on a new O2 sensor if I don't have too!

 

You've got to do the anti-fouler fix when you put on a header.

https://www.scionlife.com/forums/viewtopic.php?t=101069

 

yes thats all it is... since you no longer have a cat in your header your secondary o2 is seeing all of these HC's and CO and threw the cat efficiency below threshold code because none of it is getting filtered since you don't have a cat.... it is just because of your header, the o2 sensors should be fine, they should last about 100k miles I believe....

 

whats funny is I got this code and i have OEM exhaust manifold back until the axle back. I think my O2 sensor is greasy from my S/C (since it runs rich with the TRD tune) I cant remember if I can clean it or not, but if not, ill just replace it. I highly doubt the cat is bad, but I guess it is possible.... Hopefully its the O2 since its cheaper!

 

But bu putting the anti fouler, isn't that just "tricking" the computer? I would think that isn't the best thing. Any other way of getting rid of the CEL?

 

Technically you can with a complete stand alone, but at that point you are looking at 1700+ dollars

 

Im going threw the same issue right now, They have a new cat on order for me, apparently my insides melted, I think it leans out in high rpms which in turn causes higher exhaust temps which fries the cat, then throws the good ol' 420 code. do you have a intake on your car?

 

You seem determined not to "trick" your ecu...it'll be alright it doesn't hold a grudge...or does it??


there is another way, you get a catalytic converter welded on to your MID-pipe, you will need a REAL OBD II carb compliant cat. Most joe shmoe muffler shops will swear to you their cheapo bobo cat is(they'll tell you any thing you wanna hear)both high flow and compliant...they lie.

any who then you will need a O2 bung(lol) welded on "behind" that cat, cut your secondary O2's harness in half extend it to about 3 foot then tada! no more CEL...

by the way a real quality cat that wont crap out on you in a few months is around 200$ +, they also have some that already have the O2 bung on them already...

guess what now you just wasted 200+ on a header and your back to having a full blow carb legal cat again + the cost of the cat itself...

on the other hand a good mechanical O2 sim(non defouler type) is 25$ tops(50 if you buy WR's)

 

Just FYI, I think auto parts stors like Autozone or Discount Auto read engine codes for free, in case your light ever comes on. Just stop in, ask for someone to check the computer, and they'll let you know what it means.

I had to do it a few times with my old Saturn a few years back. Dang O2 sensor. :\

 

If you keep your stock midpipe, another CEL fix is to install an O2 sensor bung in the midpipe after the stock cat. Relocate the O2 sensor to the new bung, extend the wires as Mugetsu mentioned, and close up the O2 bung on the S-pipe with a plug.

 

I have thought about this, but do you think that little bulb cat could take the place of the main? the cat in the manifold is huge when compared to the one in the mid-pipe. I think it would work for a few months then CEL...

 

Don't see why it wouldn't work. You're still monitoring an OEM 3-way cat, so the voltage output of the heated O2 sensor should be similar whether it's checking the pre-cat or the main cat.

Having said that, I haven't read about anyone actually moving the O2 sensor behind the main cat after a header install.

If my anti-fouler trick doesn't hold up I'll consider doing this myself.

 

^^^true story...my own...

I have heard(and spoke) to 1 other person who did this, he used a real genuine replacement OBD II cali compliant cat with a built in O2 sensor. he never had a problem...BUT that still doesn't erase the fact that at that point your back to having a full blow cat in the exhaust path... now if you used a "Random tech" or Dynatech cat then you will prob keep most if not all of your headers gains.

eh we live and learn...