wats up guys i got the code P0420 i've had it for a while now but kinda put it on the back burner but lately it has been bugging the hell out of me so i did some research on it a few weeks ago and found out what the code was....

Catalyst System Efficiency Below Threshold (Bank 1)

Basically this means that the oxygen sensor downstream (after) the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs).

A code P0420 may mean that one or more of the following has happened:

* Leaded fuel was used where unleaded was called for
* An oxygen sensor is not reading (functioning) properly
* The engine coolant temperature sensor is not working properly
* Damaged exhaust manifold / catalytic converter / exhaust pipe
* Retarded spark timing

now i reset the light twice and it came back so i definitely so that this is the problem

what i want to know is should i change the cat???....if i have to change the cat i will be going with the magnaflow high flow cat since i have a apexi n1 exhaust

any input would be appreciated

 

check out the cat....unbolt the exhaust and see if the interworking of the cat is coming apart. This is probable so becuase p0420 sets when the ecu sees that the downstream oxygen sensor signal is closely representing the 1st one (switching from lean to rich). If it were me, I would put on a stock or stock-quality catalytic converter. Another trick you can try is use some spark-plug anti-foulers(found at your local autoparts store). Get 2 of them, screw them together, enlarge the holes, and screw your o2s into it. then screw it into the exhaust. this works sometimes.

 

ok cool thanks i will be unbolting the cat tomorrow once i get out of class....is there a reason why u would go with a near stock cat rather than a high flow??

 

do you want your cel to stay on? most of the high flow cats dont hace as good as substrate in them to burn all the crap thats in your exhaust.

 

Yes the computer is thinking that the cat is not working properly. However the O2 sensor that tells the computer this might be the culprit.

You might want to check for a manufactures recall for this problem. If none then get the O2 sensor checked before you jump to conclusions that it is the cat.

 

yah thats why i told him to check out the cat