Don't waste your money. I have never seen another cause for 420 or 430 than a bad cat. Do not replace an O2 in hopes of fixing this. Get the cats gutted and the tune adjusted to ignore the rears or put new cats from GM on there. Aftermarket cats will cause these codes eventually too.
X2, only a cat problem triggers this code, never an O2.Originally Posted by GasGuzzler
2001 ECSB 4x4, 5.3, Radix, 3.0 pulley, VHP Trucker cam, 216/224 .551/.551 115 lsa, 1.8 Crane roller rockers, 4L65E, Yank SC3000, 3.73, Cal-Tracs, HPTuners.
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