2021 with 59K miles. Dealer just replaced all exhaust system gaskets and clamps starting at turbo exhaust. GM has issued a service bulletin but I have not seen it. Gasket or clamp redesign? I paid $2100 for parts and labor. No easy job. This repair needs to hold up for at least the life of the engine.
2022 Refresh AT4 1500 Duramax 3.0 Diesel Check Engine Light and Exhaust Leak
- Thread starter RobertosAT4
- Start date
In spite of this exhaust/emissions problem, I like the performance, tech, ride and range of the ATX diesel. I ordered another one for July delivery with advanced tech. However, whatever fuel savings I had over 59k were reduced by $2100 for exhaust modifications. Still ahead of the 6.2l gas engine in fuel savings.
Andystoy AT4
Active member
Thanks for the update, I am surprised that your repairs were not covered by GM warranty. You should have a 5 yr/100 K warranty? The fact that GM issued a service bulletin would tend to support the warranty issue?
Teegunn
Well-known member
Thanks for the update, I am surprised that your repairs were not covered by GM warranty. You should have a 5 yr/100 K warranty? The fact that GM issued a service bulletin would tend to support the warranty issue?
I had similar issues with my 2020 AT4 3.0. GM denied coverage. The dealer had the truck 4 weeks, with many different sensors and misc repairs tried, and no fix. The bill for all this was mounting - several thousand $. Since I was working out of state when the issue happened, I was stranded with no vehicle to drive the 1000 mile trip home. I had a loaner from the dealer, but of course they wouldn't let me take the loaner out of state. I eventually traded that 2020 AT4 off for an AT4X and in the trade deal got the mounting repair bill wiped out in the trade deal. It was ridiculous that GM would not cover this issue, however.
To be clear, the AT4 3L diesel is the best driving experience in any truck I have driven or been a passenger in, including 2023 GM gasoline versions. I believe GM is committed to improving the emissions control systems reliability. How many 1500 Duramax vehicles are having the same issues? One thousand out of a hundred thousand?
Teegunn
Well-known member
I really liked my 2020 AT4 3.0. I do like my 2023 AT4X more. The 6.2 is definitely a quicker truck. And towing is about a wash. I think the extra HP of the 6.2 gives it a small advantage as it seemed that at hwy/interstate speeds pulling my big job trailer, the 3.0 had to work a little harder to pull at that speed than the 6.2. That being said, the 3.0 got around 3 mpg better on hwy's pulling the same trailer in same conditions.
The 3.0 was a great driving engine. The 10 speed transmission worked great with that torquey 3.0. MPG were probably 5 to 7 better overall on the 3.0 vs the 6.2. Lifetime on my 3.0 2020 AT4 was at 16.9 (I pull my job trailer a lot significantly lowering the liftetime MPG), the lifetime MPG at 10K miles on my 23 AT4X is currently at 13.5 (it keeps dropping the more I pull my job trailer at hwy/interstate speeds here in mountainous Montana - those mountain hwys and passes do a number on the MPG). Normal driving I would get 5 to 6 MPG better on the 3.0 vs 6.2, similar setup on both vehicles with front end level, similar sized/weight tires and wheels (6.2 actually has heavier tires/wheels by at least 10lbs per wheel).
If it weren't for the "service emissions system" issue my 2020 AT4 had that the dealer never could get fixed after 4 weeks and extensive work on it, I would still have that truck and be very happy with it. But whatever the problem was, I feel like it was likely to be a recurring problem, a problem which put the truck into severe limp mode, literally stranding you if you were more than a couple hundred miles from home. I didn't trust that engine or truck was ever going to be reliable enough for me again. I hope whoever bought it after I traded it for my 2023 AT4X in early January hasn't had the same problems popping up over and over like I did.
Sideshowdad
New member
Hi all, owner of a 2022 Sierra AT4 Duramax 3.0 with 5500km and got my first ECL emissions code. Brought it in to dealer who said all it needed was some updates (master control module etc) well one day later light is back. 
After reading all these ECL emissions issues for these trucks I'm speechless. At this rate I want out of this truck but at what cost. Also agree with others great riding truck.
After reading all these ECL emissions issues for these trucks I'm speechless. At this rate I want out of this truck but at what cost. Also agree with others great riding truck.Picked mine up in January. Drove it 2300 miles home. Have put 2200 miles on it since. Finally got word that my missing park assist sensors are available as well as the blowers for the cooled seats. Truck was built a year ago and so I figured it's time to get the oil changed. I was going to call the closest dealer this week about getting it in for those installs and the change. Earlier that day, check engine light comes on. App says it is emissions related. So I assume they will messing around with all these types of fixes that you guys have been writing about. Had been going well up to this point. Pretty happy with the truck. But having had a Honda Civic prior for 15 years with 150K miles and it never dropping a code (needed some AC work though) this vehicle costing 4z as much, doesn't give me much hope. Not taking it in until the parts for the installs are received next month.
I fear all.the local dealers are going to suck bad. Wish there was one close to me.
I fear all.the local dealers are going to suck bad. Wish there was one close to me.
Sideshowdad
New member
My ECL is gone after a few days. Holding my breath until it decides to reappearHi all, owner of a 2022 Sierra AT4 Duramax 3.0 with 5500km and got my first ECL emissions code. Brought it in to dealer who said all it needed was some updates (master control module etc) well one day later light is back.
slythetove
Active member
You can ask Onstar to tell you the codes when the truck is running btw.
I didn't keep the OnStar subscription after the first initial period. Unless it is part of the three years of data for the mapping and all that.
Do you mean how does it translate? If so what I found was this 'NOx Catalyst Efficiency Below Threshold Bank 1 Catalyst 2'
I'm taking it in on the 18th for first oil change and installation of the blowers and parking sensors. They are going to work on the issue with the code as well.
GMC AT4 Forum Photos
GMC AT4 Forum Photos
