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?
Oct 2, 2013 at 12:19 PM
