2014+ AFM (Active Fuel Management)

[sdowdy]

AFM just seems to randomly work on my truck too. I have multiple downhill stretches on my daily route. Some days it is in V4 mode with no pedal pressure/coasting, The next day it requires some pedal pressure to make it engage V4 and when I let off the pedal it goes to V8. Then other days it won't engage at all whether it's downhill or straight stretch.

 

I've found it to have nothing to do with weather, wind or what gear I'm in. It just works when it wants to.

 

It would be great if GM would give us an option to disable it completely as they do with stabilitrack/traction control.

Edited January 28, 2014 by sdowdy

[pm26]

It is astounding that they did not disable the AFM in the tow/haul mode.

[2016 Sierra Owner]

Why is it so important that the engine switches V4 to V8 or V8 to V4 at all? It's not like you are going to get any better gas mileage. I had the AFM tuned out on my 09 and did not see and change In MPG. Some of you guys act like it's the end of the world it does not switch. If it was not for the dash readout I'd never know the difference on or off.

Edited January 28, 2014 by Blue Sierra Owner

[memphistiger02]

Why is it so important that the engine switches V4 to V8 or V8 to V4 at all? It's not like you are going to get any better gas mileage. I had the AFM tuned out on my 09 and did not see and change In MPG. Some of you guys act like it's the end of the world it does not switch. If it was not for the dash readout I'd never know the difference on or off.

 

 

I just want crap to work like it should, that is why he wants to know why. That is why it is important.. you pay all of this money for a truck, you expect it work correctly.

[2016 Sierra Owner]

I just want crap to work like it should, that is why he wants to know why. That is why it is important.. you pay all of this money for a truck, you expect it work correctly.

Ok what is correct and what is not correct operation then? Can you tell me that? I mean not long ago a V8 was a V8 all the time and nobody complained. Everyone here has a different story about how their AFM functions and if you just let it work with watching it all the time the truck will run just fine. That's all I'm saying.

[memphistiger02]

I don't know how it works, I didn't design it, but a correctly designed piece of equipment should work consistently... correct?

 

[2016 Sierra Owner]

Yes you are correct. However with everyone here having a different story about how their AFM works. You would think that would not be the case.

[kstruckcountry]

A well designed piece of equipment will adapt to the conditions it's used in. Which is what the truck is doing by deciding to or to not go to V4...

[memphistiger02]

Mine seems to switch at weird times and almost feels like the trans is slipping. I am hoping that whenever they actually fix my recall for the computer it will fix this as well. Right now my truck is dead in the chevy garage because when they went to upgrade the computer system I guess it crashed. Now they are waiting for Chevy corp to call them in a new code was the story I got.

[pm26]

I don't know how it works, I didn't design it, but a correctly designed piece of equipment should work consistently... correct?

Well, it does, it consistently malfunctions.

[sdowdy]

"""A well designed piece of equipment will adapt to the conditions it's used in. Which is what the truck is doing by deciding to or to not go to V4..."""

 

 

I agree, it should adapt to changing conditions. What is the condition that would cause it to stay in V8 down a 1/2mile stretch, I'm guessing 5-7% grade? Some days it stays in V4, some days it stays in V8.

 

The system is random, it's not consistent day to day or during the same conditions. I've had the fire recall so I'm assuming my truck is up to date on the rest.

[kstruckcountry]

I don't know much about the V4 mode. All I know is that like other fuel saving measures on pickups (crappy tires, spoilers) it makes little to no difference. A lot of people who have disabled their AFM say their mileage did not go down.

[Silver space ship]

Why is it so important that the engine switches V4 to V8 or V8 to V4 at all? It's not like you are going to get any better gas mileage. I had the AFM tuned out on my 09 and did not see and change In MPG. Some of you guys act like it's the end of the world it does not switch. If it was not for the dash readout I'd never know the difference on or off.

I can only speak for myself but but truck gets way better milage in v4 then v8.

[2016 Sierra Owner]

Well yeah my wife's 4 cyl equinox gets better mileage than my truck. However I bought a V8. You could always get the Range module that keeps the truck in V4 longer if you are worried that much about gas mileage. I bet if you didn't look at the dash light that says V4 you would never know it was on. Maybe they need to do away with that light like the 4x4 engaged light.

 

http://www.rangetechnology.com/pages/v4

Edited January 29, 2014 by Blue Sierra Owner

[kelub]

Mine seems pretty consistant. I use the cruise control a lot commuting back and forth to work, and I've noticed it seems to sort of anticipate what I may or may not need, because when I go into cruise it usually drops to V4 pretty quick. I assume it's because I'm establishing that I intend to go a consistent speed vs the potential inconsistency of using my foot. I also see it drop to v4 after a few seconds of not accelerating - again, I think it goes back to a consistency thing. If the truck anticipates you're going to need to accelerate, it's going to try and provide maximum torque. If it thinks you're going to be varying your speed or elevation a bunch, then it'll stay in V8.

 

And since it is a learning system, maybe your past driving has "taught" it to stay in V8 more frequently due to shifts in speed or elevation or something. Not sure there, but I don't think it's a straightforward "if I do <X> then it drops to V4."