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Surprise results after disabling DFM on my AT4X 6.2

I’m new to using forums. I never post or have done social media but it seems the only way to get the best answers. So if someone could please tell me if they have found a good tuner for a 2025 1500 AT4X with a 6.2 I would appreciate it.
 

Padrino said:
I’m new to using forums. I never post or have done social media but it seems the only way to get the best answers. So if someone could please tell me if they have found a good tuner for a 2025 1500 AT4X with a 6.2 I would appreciate it.
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Welcome.
 

goatspeed said:
I roll a 2023 AT4x half ton and I recently decided to disable the autostop by way of a Carbyte. This little device sticks on your diag port just north of your hood lever in the cab. It also disables DFM/AFM which wasn't really a selling point for it for me...I just wanted the autostop stopped without pushing the button every time I drove. So a week now into having DFM disabled I have some impressions of being in full v8 mode all the time and I wonder if anyone else here has gone through this. This isn't really an AT4X specific thing obviously. But here we are.

So first impression is that we must be in v6 mode ALOT. Without knowing exactly when cylinders are shut off prior to installing Carbyte, I would have assumed were are always in v8 mode, and then if we get on the highway and set our cruise etc, it might toggle down to v6 and v4 mode if possible. In fact, v8 all the time makes my truck a completely different animal. Accelleration at any speed is faster. I should really do a 0-60 from dead stop with DFM enabled and then disabled for better science, maybe I will when I can get at some non slippery roads (Minnesota winter). I've had to adjust how I step on the gas at a stop light because I've nearly lunged into the car ahead of me a couple of times now. Without any good science, my impression is that I was running in v6 mode almost all the time. And the at4x is now a sports car.

On the topic of mileage, obviously there is a massive swing there. In pure city driving, I barely get above 10mpg. Mixed driving gets me to around 14mpg. And on a long trip where I was able to use the cruise at a modest 65mph, I was at 15.7mpg. Before, those numbers were 12/14/18 mpg respectively. For reference, I have no lift/leveling other than factory. I do have 295/65/r18's on it which is roughly the same height as factory, but 2 cm wider.

Now I really don't care about mileage. When I get a truck, I lift it, put big tires on it, add a grille guard etc...and immediately give up 2-3mpg for the sake of awesomeness. It just so happens this time around I didn't need to do anything to my new truck because it's an AT4x. But it would seem that without DFM/AFM, the 6.2 is almost unusable for most because we go back to 1990's fuel mileage. But I can't stess enough...my truck is now a completely different animal. Anyone else disable DFM and have similar observations?
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Is driving in L9 similar to effects of Carbyte?
 

I had the device installed and the reduced engine braking was too significant for my taste. As a side effect for some reason my brake pedal then became quite stiff like really had to put my foot into it which was unexpected.

I'll be returning mine but I could see why people would want it. The gas mileage was also atrocious going from ~340 mi per tank down to ~250, not a huge deal for me but thats a big drop.

EDIT: I am in contact with the company to discuss these issues but less interested in keeping the device that did this or trying a different unit given this experience.
 

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cynistersix said:
I had the device installed and the reduced engine braking was too significant for my taste. As a side effect for some reason my brake pedal then became quite stiff like really had to put my foot into it which was unexpected.

I'll be returning mine but I could see why people would want it. The gas mileage was also atrocious going from ~340 mi per tank down to ~250, not a huge deal for me but thats a big drop.
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Your saying this device that turns off auto start/stop and the DFM , that it somehow affected your brake pedal feel?
HOW!!!!
You don't install it you just plug it into the OBD port, has nothing to do with the brakes at all......
 

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hdrolling said:
Your saying this devise that turns off auto start/stop and the DFM , that it somehow affected your brake pedal feel?
HOW!!!!
You don't install it you just plug it into the OBD port, has nothing to do with the brakes at all......
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The computer has EVERYTHING to do with what goes on with modern vehicles. How to you think stability control works? The computer is able to apply brake pressure to individual tires to control stability. Computer is accessed by OBD II port.
 

Viking Truck said:
The computer has EVERYTHING to do with what goes on with modern vehicles. How to you think stability control works? The computer is able to apply brake pressure to individual tires to control stability. Computer is accessed by OBD II port.
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If his device is somehow controlling engine braking and brake pedal firmness then he needs to be contacting them for a new one, this is not what the deice does and has nothing to do with those areas. Just because it has to do with the computer doesn't mean this can access those areas.

I suppose its also going to start steering the truck since the computer controls the lane assist?

That is not what this device does, it turns off the DFM and the auto start/stop and that's it, but it can read and clear codes.
What does the DFM or auto start/stop have to do with stability control?
 

A corrupt file load to the chip could cause all sorts of crazy things. Without knowing how the ECU is programmed at the code level, all we can do on this form is speculate. And I doubt anyone with working knowledge of the ECU code would dare Juban to a forum like this to answer it, and understandably so.

Myself, I would contact the manufacturer and see about a replacement.
 

hdrolling said:
If his device is somehow controlling engine braking and brake pedal firmness then he needs to be contacting them for a new one, this is not what the deice does and has nothing to do with those areas. Just because it has to do with the computer doesn't mean this can access those areas.

I suppose its also going to start steering the truck since the computer controls the lane assist?

That is not what this device does, it turns off the DFM and the auto start/stop and that's it, but it can read and clear codes.
What does the DFM or auto start/stop have to do with stability control?
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3 plus years ago I ordered a Jeep Wrangler 392 with a Hemi V8 in it. Before it arrived I ordered a device called a Tazer for that vehicle. The purpose of this device was to be able to change tire size so the speedometer was accurate, customize DRLs, turn off certain nanny state safety features and several other things. A couple of years later with updates this device is able to control braking to act as an anti-theft device and force the vehicle into 2wd even though it was designed for full time 4wd mode. Once a device has access to the computer it just needs firmware updates (or programming errors) to cause all sorts of acts that it was not designed for. And, if the vehicle is capable of steering inputs that is also possible. Neither my 2024 GMC or 2021 Jeep is, they only warn of lane departure and cannot correct.
 

I just traded in my 22 refreshed AT4 6.2 for a 2025 AT4X with the 6.2. I decided I didn’t want to roll the dice on the recall. I have been a DFM and then AFM hater for a long time. I used the Range disabler on my 2015 and 2018 Sierra 6.2s and when no longer effective on the 22 refresh I drove around in L9. Every time I start out I go through a flow like I am starting an airplane…shifter M, paddle up to 9, start/stop button off. I didn’t do this for engine durability, I have been told the lifters will fail despite this and I never keep them that long anyway. It was the bogging down, hesitation and slight vibration I felt when kicking in that I hated. But for the life of me I cannot hear, feel or otherwise notice it on the new truck. Even in “sport mode” with the exhaust opened up I notice nothing. Either it is not engaging in this truck or they really improved it. No more L9 for me. Now the start stop…..
 

prfalcon said:
I just traded in my 22 refreshed AT4 6.2 for a 2025 AT4X with the 6.2. I decided I didn’t want to roll the dice on the recall. I have been a DFM and then AFM hater for a long time. I used the Range disabler on my 2015 and 2018 Sierra 6.2s and when no longer effective on the 22 refresh I drove around in L9. Every time I start out I go through a flow like I am starting an airplane…shifter M, paddle up to 9, start/stop button off. I didn’t do this for engine durability, I have been told the lifters will fail despite this and I never keep them that long anyway. It was the bogging down, hesitation and slight vibration I felt when kicking in that I hated. But for the life of me I cannot hear, feel or otherwise notice it on the new truck. Even in “sport mode” with the exhaust opened up I notice nothing. Either it is not engaging in this truck or they really improved it. No more L9 for me. Now the start stop…..
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Interesting. I absolutely feel the bogging down/hesitation/vibration/shuttering in my '25. At first I feared it was indicator of engine issues many warn about as I was unaware it had DFM, though I suspected as such and came across this forum and learned of Carbyte or running in hi-low. L9/10 seems to eliminate it, but I've only been running that for about a week. I don't mind the extra steps. 80-90% of driving is around town, but for longer road trips, I don't mind hwy cruising as designed for improved mileage. In short, it is frustration having to go through any steps to get the full use/power of the engine I paid for. At least GMC is still offering hearty V8s, regardless of having to manipulate system to use it. :) (to answer another comment, when I run in low, the AFM does not seem to kick in, so far, even though light on switch shows it's on)
 

I picked up the range DFM disabler that plugs directly into the ecm in front of the front driver tire so my obd port is still open for use. Never had any issues or brake changes. Gas mileage went down but that was expected.
 

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