chad.bawden

I recently had a check engine code come on. Autozone said it was code # P0420. They told me to clean the mass air flow sensor. Is that the correct thing to do?

h0p3l355dork

I googled that code and (had it before as well) and I believe it has to do with the catalytic converter and more specifically the O2 sensor. You might need/want to check that out.

chad.bawden

Thanks I will check that out and hopefully it is something small

philafelman

catalyst deterioration.....most likely need a new cat.

j3wman

autozone says a lot of things. its a cat, its a generic code so its gonna be the same across the board. it said cat when i looked it up too.

92civlude

I agree with Philafelman. A P0420 is catalyst deterioration. You most likely need a cat. You should also look into what caused the cat to fail.

sgraham01

you need to verify that your rear o2 sensor's reading is fluctuating properly. If the post-cat o2 sensor is bad, you can get that code since the computer thinks the post-cat exhaust's o2 content is out of range. A live data scan tool can monitor rear o2 sensor voltage, and that needs to be checked before you change the cat out. I would run it by a reputable repair shop and have them check it. they may charge you a few bucks, but it may be worth it.

Pauly321

I had this exact same code. Try clearing it and seeing how many miles you can go without it coming back on. I used to be able to go hundreds of miles before it came on, usually when I was gettting on the car. It has now gone off and hasn't came on in about a thousand or so miles.

chorizo4rmdtown

need to install a 02 fouler more like your car has a aftermarket cat and the o2 hate those goggle at o2 fouler a you can pic one up at autozone for like 5 bucks

Atomic1

Before you waste money on a new cat, please check for exhaust leaks at all joints from the headers to the cat. A small leak at any of these joints can cause a p0420. I know, I learned the hard way and listened to all the folks saying it had to be my cat....replaced cat and the code came back. After I got pissed and tore into the exhaust further I found the small leak only by removing the A pipe and inspecting the gasket.....now good to go.

If you dont find any leaks and the cat visually looks ok, then try replacing the secondary o2. Still issues, then replace primary o2. Last option is to replace the cat...they are EXPENSIVE.

skracer13

Atomic 1 is correct, a leak will cause a P0420 code. 90% of the time a P0420 would come after a P0137, P0138, or a P0141 Evaluate before spending your hard earn money.

361 accord

ive had this, first i replaced both sensors, that worked for a few thousand miles, then had to replace the cat cuz a more specific code for cat deficiency

Atomic1

When you replaced the cat, did you also replace all the gaskets?