2003 Chevrolet Impala PO420

Tiny
FAW484
  • MEMBER
  • 2003 CHEVROLET IMPALA
  • 92,000 MILES
I have a 2003 Chevy Impala with a 3.8 V^. Back a couple of months ago my check engine light came on and there was a code of PO420 so I went with the cheapest way and replaced the O2 sensors with genuine ACDELCO brand just like that came on the car. The a week later the light came back on with the same code and I had the Catalyst replaced and it ran good for a couple of months. Then yesterday the check engine light came back on with the same code of PO 420. So I took it to the muffler shop and had them check for any excaust leaks and there wasn't any. Can you tell me what else could be wrong?
Wednesday, October 2nd, 2013 AT 12:19 PM

1 Reply

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Just because that code is set doe'st necessarily mean it is the problem. Check for damaged O2 or wiring leading to O2 also check for holes in duct work on intake an vacuum leaks. It can also be a small exhaust leak
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Wednesday, October 2nd, 2013 AT 1:09 PM

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