P0420/p0430

apextc

I want to resurrect this thread as I am having the same issue.

Situation: I am getting a P0420 / 0430 error code.

My car: 2009 Sport / MT/ 79K with ONLY bolt-ons which are Takeda Intake, Full Stillen Dual Exhaust System.

I got the car checked at a mechanic and in summary, it seems like its a step by step process to figure out the root cause, which is to TRY:

1- change 02 sensors
2- Buy a check engine light eliminator from BLOX racing
3- Take it to a trusted performance shop

Anyone in the Chicagoland area/Naperville help a brotha out?





What causes the P0420 code?

Damaged muffler or leaks in the muffler
Damaged exhaust manifold or leaks in the exhaust manifold
Damaged exhaust pipe or exhaust pipe leaks
A misfire in the engine
Oil contamination in catalytic converter
Faulty catalytic converter (most common)
Faulty engine coolant temperature sensor
Faulty front oxygen sensor
Faulty rear oxygen sensor
Damaged oxygen sensor wiring
Oxygen sensor wiring that is not properly connected
Damaged oxygen sensor connectors
A fuel injector that is leaking
Fuel pressure that is high
Use of the wrong kind of fuel (using leaded fuel instead of unleaded fuel)

Wilson2608

This is a cat code correct? Kinda odd since your still using stock cats. I'd either say a clogged cat or sensor. Before buying any "code elimination kit" I'd check for other solutions. If you want to eliminate the code forever get uprev as they can do it on that software + you get a tune.

__________________
Stillen G3, z1 Intake Manifold, Stillen Headers, Z1 HFC's, Stillen Catback. 330whp 267 ft- lbs tuned at Z1 motorsports.

Jhill

I'm not sure if your asking what causes a p0420 as in what causes the code or what cause the cat to go bad causing the p0420. From my experience (12 years as a diag/ drivability tech with different car lines) a p0420 code is almost always a failed cat, I can't think of anytime it has not been, that's not the same case for a diesel but on a gas engine it's almost guaranteed (I say almost for the 1 out of 1 million it isn't).

Of your stuff above
Muffler- no as that is after the o2 sensor
Manifold crack- you will have lean code (even though it will actually be rich)
Exhaust leaks- again after the o2 so no
Misfire- obviously have misfire codes
Oil- never seen this even on oil burners and most likely would be damaging the cat so once again its bad cat
O2 wiring or conn- going to have o2 codes (inactivity)
Injector- rich code
Fuel press- rich code

I have really never seen a p0420 and it not be a cat (for gas engines), the manufactures basically test all other sensors first and veryify they are functioning correctly before they will run a cat test and throw a p0420.