Can't find where Dodge will extend Warranty coverage to fix a bogus fault code?

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I have a P0420 Fault Code on my '06 Dodge Ram 1500 Hemi. Repair Pal said that some O E's, including Dodge, will fix it for free! I can't find further info anywhere on this site.... even though it says it is on here. Any help? I don't want to start replacing expensive parts if there's nothing wrong with them and the fault keeps coming back. It has been running a little rough lately. But the fault came on right after my last oil change. I used the Lucas SENTHETIC Oil Stabilizer this time. I have in the past too, with no problems. And just the regular Castrol 5W-20.