Codes p0420and P0430, Catalytic Converter?

Tiny
MATTANDALLIE
  • MEMBER
  • 2019 CHEVROLET EXPRESS
  • V6
  • AUTOMATIC
  • 75,000 MILES
In June my car developed a leak at the clamp where the Y pipe meets the engine. I took it to a mechanic who replaced the whole pipe. I began having issues with misfires, and the o2 sensor they installed was faulty, so I took it somewhere else. They replaced the newly replaced o2 sensor and all was good.

In September I began intermittently receiving codes p0420and p0430 for both catalytic converters. No other issues. The car was running smoothly and perfectly. I took it back and had the car checked thoroughly. Had catalytic converters replaced under warranty.

Immediately after replacement, the car started whistling and losing power. No code but it had been inspected by 2 independent mechanic shops who said there was nothing else wrong and that it was a catalytic converter. Has it replaced again and immediately off the lot was whistling and sluggish. This is the third replacement in under 30 days. Each time it goes bad within hours and has significant blueing.

There’s no code and when the converters are removed, it runs perfectly. All of the tests show nothing wrong. I took it to both a general mechanic and one who specializes in engines. Both say the issue is in the catalytic converter. We had the fuel injectors checked Live test. We had the engine checked over thoroughly. We haven’t gotten any misfires or fuel trim codes.

Today we took it back for another warranty replacement. The shop said they got a faulty MAF code. However, I dropped it off with no codes, no lights. There haven’t been codes or lights the entire time.

Is it possible the MAF is the issue? Or is the code (p0101) a symptom of the clogged converter? Or is the MAF failure what’s causing the converters to go bad? The dealership won’t even touch it because of the aftermarket catalytic converter install, and I am out of ideas and out of money.
Thursday, December 14th, 2023 AT 7:21 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,840 POSTS
Yep, first the whistling noise sounds like the old catalytic converter material is stuck the muffler, the second problem is the aftermarket cats, they are cheap and don't work well and the computer can tell. Also, the MAF sensor can cause an issue with the air/fuel mixture which may overload the cats. I would get an OEM MAF and cat system to fix the problem. Sorry I know this can be expensive, but this is why factory parts can work better. Here is how to do the job correctly so you can see what needs to be done or if you want to try the repair yourself.

This video will show you how:

https://youtu.be/CORe9JyrexI?si=VZ-lff0mIUXmTmuP

here is the MAF sensor replacement. Check out the images (below). Please let us know what happens.
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Thursday, December 14th, 2023 AT 4:48 PM

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