On page 176 of the owners manual there is a chart for gear vs down shift gear... I wonder if the programming is wonky and thinking you're going into M mode instead of increasing range

 

the "limit" part means the highest gear itll let you go. so say you put it in manual and set it to 4th gear. it will start off in 1st, and make its way all the way to 4th gear and it will ride 4th as high into the rpms as you let it and wont shift out of 4th. its not a true "manual".

 

Great, something else to add to the growing list possible problems with the truck we don't even have yet.

I use the "L" feature and manual shift also, all the time. It is a great feature, especially if towing uphill and you are behind a line of cars & you want it to hold a gear, because the speed is causing the transmission to constantly upshifting/downshifting. It keeps your transmission from overheating. VERY IMPORTANT when towing or offroading.

 

Did you ever get this resolved?

I just had a related issue pop up on my 23 Trail Boss. In my case, the +/- buttons simply do nothing. When I make the shift into L, it will react as expected (it will shift or not, according to the chart in the owner's manual) but then I'll have no control with either button. This started a couple days ago, and it's been an issue maybe 4 of 5 times testing it. No idea what kicked off the issue. Haven't been to the dealer yet.

 

2024 ZR2 (1,700 miles) I'm here because I am having the same exact issue and have been able to recreate it multiple times. I'm still doing some testing to see if it has anything to do with the anti collision system or "lane keep" features. I'm not saying either of those would cause the issue, but I'm just can't understand what else would cause the system error. If I'm driving and shift into "L" it will drop one gear (which is normal), then if I want to go down a gear or up, pressing the +/- buttons will either do nothing or do the exact opposite (pressing the "+” button will downshift. Pressing the "+” button again will downshift again). I've never experienced this in any other vehicle before. I've also never driven a newer vehicle with so many different sensors and such, which could be causing the issue. If I can't, or anyone else can't, determine what the issue is, I'm going to go to the dealership.

 

If I can't, or anyone else can't, determine what the issue is, I'm going to go to the dealership.

I'm thinking the same, time to reach out to the dealer for me. I've now experienced all sorts of combinations - the buttons doing opposite of what you want, both buttons causing downshift, and the buttons simply doing nothing. Can’t find a cause or correlation.

 

It really seems like everyone misunderstands how "L" and the range selector buttons work.

 

It's understood that if in "L" the highest gear selected will be the last gear the transmission shifts to (if in L4, from a stop, it will go through 1st gear to 4th gear and not shift into 5th) until either pressing the "+" button to increase to L5 (fifth gear) or if shifted back into "D".

The issue is, when pressing the "+" button to increase to L5 it will either do nothing or downshift to L3 which is displayed on the screen (and felt). That doesn't seem to be normal.

 

where you on the breaks while hitting +? maybe since you upshifted a higher gear, the engine breaking feature kicked in and down shifted since you had break pressure applied and were slowing losing speed. thats the only thing i can think of.

 

Appreciate the thought but my issues are visible in the number next to the “L” in the DIC. I was saying downshift, but I maybe should have said “reduce the upper gear limit” or such. As far as I understand the + button should make that number go up, the - should make it go down. My truck did that for many months. Now it rarely does.

 

It is possible you have a malfunctioning + and - button. May or may not be installed or produced properly also. I would certainly take it back to dealer.

Also, is it possible that once you set the top gear while in L, do you have to go back to Park or Neutral to reset the top gear, or should you be able to over ride the top gear by using the + & - buttons ?
Is it different than being in L and shifting through each gear vs setting the top gear ?

Technology is great but only when it is working properly.

 

I am having the same issue, I have a brand new 2024 GMC canyon at4. It has 2600 miles and I noticed mine will do this as well. I first thought it was something I did wrong. Mine does it nearly every time I try to shift in manual. I thought I did not have it pulled all the way back as the next few times I tried to recreate it it seemed to go away. But no it is random and not good when you think you are going to upshift only to down shift with a very high rev.

 

Have you taken it to the dealer? I took mine in and they said they couldn't recreate the problem, so I came back with a video of the problem, they still say they haven't seen it before. SMH

 

I never took mine in. The problem has mostly gone away for me lately. Not sure if it was the software update from the fall, or colder temps (dunno how but maybe?) or something else. I’ll mention it next time I’m at the dealer anyway to get more records of this issue.

 

Mine has done this a few times also, i wonder if it's because the hill descent is on?

 

I just have the basic work truck with the TurboTax motor and trans combo, so I don't have any of the fancy electronics. I personally think it's a defective TCU because mine has done it at a complete stop.

 

On mine I notice if I wiggle the shifter a little towards D and back to L, the button starts working fine.

 

I'll have to try that, but these trucks are too new to be having to do any kind of "wiggling" those are old truck problems! Lol

 

Has anyone gotten a GM or dealer fix to the issue of the +/- limit issue where the + actually shifts down while driving in L? My dealer says they haven't seen the problem with other vehicles and I really don't want them doing 'trial and error' on my 2024 Denali Canyon.