JohnH4260

Maybe try using a Battery Tender?

Thank you for posting this update.

9,089 miles on my 2021 GMC Sierra Denali. It’s been a great truck and fun to drive.

I never activated my On-Star account during the 3-month trial period after initial purchase. And then it expired and I haven’t heard a word about it since leaving the dealership. My phone is my On-Star.

Sorry to hear about your accident… I hope everything works out in your favor.

Been using 91 (premium), since buying my truck in March 2021. Currently averaging 15-15.5 mpg around town. I disable stop-start after ignition and drive in L7 around town. So-far-so-good in terms of fuel consumption and what I was expecting when I purchased the truck.

I had 3M window protection film installed on my windshield right after buying my truck. It’s been over 1 year and no problems so far. Also had it installed on my 2015 SUV and trouble free as well.

Can you post a photo? Thanks.

Yes, I do the same thing, drive in L3 through L9 since I purchased the truck in March 2021. Also disable the auto stop/start every time I drive. So far, so good.

I’d buy a supercharged V8 if it was offered. We’ve owned a new Land Rover Range Rover Supercharged V8 since June 2015. It’s rated at only 525hp and definitely has the power to take off and move right along. And the fuel economy currently reads 18.5 mpg on the long term gauge. Only problem we’ve had was a leaking AC Freon hose that was replaced under warranty. And 8 cylinder power all the time, no Dynamic Fuel Management bullshit.

It seems the 2019-2021 GM trucks (Sierra and Silverado), are plagued by two major problems. The first is lifter failure which may be attributed to DFM (dynamic fuel management), the lifters, or a combination of both. The second is a leaking rear window. If you search the forum, you’ll find information about both problems.

Ordered my 2021 GMC Sierra Denali in early January 2021. It was built in Ft. Wayne, IN, and delivered to me on March 20, 2021. So far, no leak on my rear sliding window.

The images below are from pages 352-354 in my 2021 GMC Sierra owners manual. In the engine compartment fuse box, it shows #60 and #67 are the Active Fuel Management 1 and Active Fuel Management 2 fuses. Maybe there’s another system involved as well.

After receiving my truck in March 2021, I cut the flapper spring and fixed the valve in the open position with 2 hose clamps. A few others have done the same and posed photos on the forum. I don’t know if it has done any good, but it won’t fail.

I’ve been using Costco 91 octane gas since new in March 2021. No problems so far…