P0420 catalyst system low efficiency


now i got this trouble code a couple of days after putting on an ss/sc downpipe with a high flow on my 2.2 right now i have the ss/sc manifold, ss/sc downpipe with a vibrant 3 inch catback so you think mine came on because ive lost to much back pressure with the vibrant catback
thanks

 

i got that along with 2 other codes..i tune it and havent came back

 

i would but i got a 2.2 so no tuning

 

dat sux...

 

I'm a bit confused. Do you have an SS/SC downpipe with the SS cat, or an aftermarket downpipe with a cat?



Oh, and the cat-back won't throw that code.

 

sounds like you bought a bum ss/sc downpipe. Could have been plugged before you got it.

 

its an ss/sc downpipe with an aftermarket highflow cat

 

its the downpipe and the cat. the sensor is reading too much air flow causing the code

 

get a o2 sensor spacer and your done.....

 

most likely what it is.

 

alright im gonna try the spacer has anyone else with a cobalt tried this or am i gonna be the first 1

 

i did it for hockeyman. it set another code at first but cleared them and its been running code free for over 3k miles

 

How do you clear a code? Dealership? I installed a ZZP downpipe no cat and I got a CEL but I have no idea what code it is...

 

nice is it the same 18mm plug fouler spacer from HELP that fits

 

Its the P0420 code that is telling you that the cat is inefficient. Of course in your case, it is non-existant. You can turn it off with HPtuners I believe.

 

Not on a 2.2 you can't.

You can clear the code at any autozone or Murrays or any auto parts store using an ODB-II scanner but problem is if the code default again three times it will trip the check engine light.

Moving the o2 sensor may help but I believe the real solution would to just put the stock system back on for now till you can find a more managed approach, that or run an interceptor in your car to clear the code everytime it comes on

 

Well, I can live with the CEL. I definitly wont be going back to stock. Do you think if I went to get my stage 2 they would clear the codes and re-flash my ECU to include all my mods?

 

I was refering to Micone's post.


The stage 2 tune wouldn't include your mods. You would have to get a custom tune for that.

 

I killed my cat and got the same code.

 

Spacer works fine. The only thing you may have to do is cut a square out in the body where the sensor is so it will fit with the space. That's what I had to do. Spacer been in for 2 months now and no more code.

 

well, I appreciate the info. I will start searching for a custom tuner then.

 

im using my interceptor on my 2.2 to clear cel for the downpipe so for ive on clearedc once and it never cam back on (po420)

 

Do a couple of WOT runs and see if it comes on again.

 

if you run a DTC check you will see it still stores the code till it reaches 3 faults and then the CEL will come back on again.