Check engine light p0420 code just replaced Catalytic converter two months ago.?

Question

So I was driving and out of nowhere my check engine light came on the code P0420 came on When I scanned it I’m confuse weather is an O2 sensor or something else that may be causing the code I’m wondering if it’s the catalytic converter breaking into t when I scanned it I’m confuse weather is an O2 sensor or something else that may be causing the code I’m wondering if it’s the catalytic converter breaking into car. I clear the check engine light and it has come on in the week does anybody know about this

Dan · Answer

Not the O2, cat was likely cheap aftermarket. The new cat must have a label that says it's approved for use in California even if you live elsewhere.

FlagMichael · Answer

The most common cause of P0420 codes, in my experience, is an exhaust leak ahead of the converter. A muffler shop can check that for you at a reasonable price and fix it if necessary.

Another common contributor (never a flat-out cause on a new converter, in my experience) is dirty fuel injectors. If you use whatever gas is cheapest it can be a real issue.

thebax2006 · Answer

If your car is a VW you can't use after market catalytic converters. You must use a factory converter.
The only after market converters I use a re Walker brand converters. They have a 75% success rate for not triggering the P0420 code again.
It's not 02 sensors. The fact the P0420 code is setting means the 02 sensors are working.

Clark · Answer

They cleared it at a shop hasn’t come on for like a week

Anonymous · Answer

Replace the rear O2 sensor with a factory (OEM) sensor.  Clear the codes.  No fix, time to see a mechanic with a scanner.  If you installed an aftermarket converter, that could be your problem.

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Check engine light p0420 code just replaced Catalytic converter two months ago.?

5 Answers