P0420 and P0430
Thread Starter
5th Gear
Joined: Feb 2025
Posts: 5
Likes: 0
P0420 and P0430
If I have these codes and will it be the upstream o2 sensors or downstream? Im trying to replace just to see if its just the sensors that are bad or my Catalytic converters. Ls2 2007 C6. Thanks!
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,410
Likes: 3,964
From: Cape Coral, Florida
Get your car professionally diagnosed instead of throwing parts at it…doubt both O2’s are bad and if it is your cats that is an “effect” and not a cause…cats just don’t go bad.
Team Owner
Joined: May 2000
Posts: 53,567
Likes: 5,582
From: Plantation Florida USAF(Retired) 1966-1990
U.S. Air Force
St. Jude Donor '05 thru '26
NCM Sinkhole Donor
I had the same problem and it turnout my right cat was clogged, I took it to a muffler shop, left cat registered below 200 degrees and the right over 400 degrees, had the right cat changed no more light.
