tbarn

GM filled it. If it ain't leakin', it's still full. That is the theory. They could give a rats ass about the dealer.

Not judgin" cuz I really don't car what refrigerant you use but read this to start. End Users Switching R-1234yf Vehicles Over to R-134a - Refrigerant HQ

99.9% of the time P0420/30 is a bad cat. You're making it more expensive and harder than it needs to be.

Ah man. Been there. Broke a couple of those at the dealer when popping door panels off. It ain't hard. I looked high and low but I cannot find any. I used to take them off and save them when I turned a warranty latches in. Must have left them for the next guy when I retired.

Ethanol free 91 is all we have around here. It's all I use for mowers, blowers, etc.

Definitely have to remove pan. What you see is just a pass through connector for the sensor in the pan.

I don't think there is a whole lot of function the aftermarket can add to a Denali.

I think the dealer is lying or it is a dealer trade and they did not know. It sure ain't factory. OP, what dealer is listed on the window sticker? Is it where you bought it?

Pull it out and throw it in the trash.

GDS does not do programing. Diagnostic tool only. Also, GM dealer cannot do custom programing for you.

I vote lifter/cam

Something like this.

Will have to go to a dealer and get another cluster or send in yours to get reset. Dealers can order clusters with miles pre programmed or "0" miles. When they program the cluster they need to add the current miles if known. I wouldn't worry about a few thousand miles, but 50k is a LOT. Some (all?) states offer a sticker to add to the door jamb to correct any miss information on the cluster.

Have it on my Blazer. Hate it. Never use it. Can be turned off for regular mirror usage. But I wear trifocals, sooooo. Maybe for someone without glasses or single lens.

From purchase date of policy.