Found AFM Workaround (8-speed)

AllTerrainX · October 12, 2016

Hi everyone,

I just purchased a 2016 GMC Sierra SLT Crew Cab All Terrain X a few weekends ago. The AFM (Active Fuel Management) is such a pain when switching from V4 to V8 mode at low speeds (non-highway driving) because I hate the "bogging" or "hesitating" feeling the truck gives off and the exhaust tone is UGH...

I had a 2007 Avalanche and used a Range Technology device to disable it. But overtime I would have to pull the device out and plug it back in because it wouldn't activate sometimes. Been reading on this forum about the Range device for the newer Sierra's and people have been having issues with them and could mess with the computer overtime. So I won't be going that route.

Another option is to get a tune like BlackBear and get it disabled or set a minimum speed of when the AFM activates. But a tune isn't an option for me right now because I want to keep my warranty as long as I can. Someday BlackBear tune will in my future!

So I decided to try something. For the last couple days I have been driving in Manual mode "M" and setting it to M7 (7th gear) and driving like normal (non-highway driving). I was shifting gears up ( + ) and down ( - ) because I thought that was what you were suppose to do but I found out I can just set it to M7 and not worry about shifting, it does it for me, it just doesn't go into M8 (8th gear), which I don't need when I am going less then 50mph most days. I watched it stay in V8 mode stay the WHOLE TIME! The only time it went into V4 mode was when I shifted into M8 and then I switched back to M7 and it went back into V8 mode. So I think I found a workaround without having to void my warranty with a tune or messing up my computer with a AFM disabler device.

I want to get your thoughts guys, will running in Manual "M" mode ruin the transmission in anyway? Not using M8 (8th gear) for slow speeds have long term affects with that gear?

I am going to do this for another week or two and report my findings.

This guy is happy when my truck isn't "bogging" or "hesitating" and have full power!!!

Silvern Sentry · October 12, 2016

this is old just fyi

AllTerrainX · October 12, 2016

this is old just fyi

Do you have a link to a post I could read? I searched the forums for days and couldn't find anything about Manual mode versus Disabler/Tuners.

Dnt · October 12, 2016

Thanks for posting that. I have seen the M7 drive mode mentioned before but your details are going to be helpful to some people.

emeryz28 · October 12, 2016

I tried this, wasn't a huge fan. Got a Diablo Tuner, disabled AFM, did the 91 octane tune and noticed my MPG go up by about 1.3 and the drivability improvement was through the roof with it not always dropping to V4

AllTerrainX · October 12, 2016

Thanks for posting that. I have seen the M7 drive mode mentioned before but your details are going to be helpful to some people.

Thanks MyFavTruck. I did some searches for M5 and M7 and couple things came up of some mentions of it but nothing more really. I'll add some more tags to this topic.

I tried this, wasn't a huge fan. Got a Diablo Tuner, disabled AFM, did the 91 octane tune and noticed my MPG go up by about 1.3 and the drivability improvement was through the roof with it not always dropping to V4

emeryz28,

Can you explain why you are not a fan of this? Just going into "M" and setting it to M7 before you drive seems easy enough.

cbrsilv15 · October 12, 2016

This may be a dumb question, but how exactly do you put it in m7 mode? Put it in manual mode, go to 7th gear and drive it like that?

Silvern Sentry · October 12, 2016

manual mode is range mode.

ie. if in 2nd will use 1 & 2. If in 5 will use 1-5.

the manual has more info

AllTerrainX · October 12, 2016

This may be a dumb question, but how exactly do you put it in m7 mode? Put it in manual mode, go to 7th gear and drive it like that?

No such thing as a dumb question, we are here to learn And yup, go to M7 and drive, no need to shift up and down after that. It just will never go into 8th gear unless you shift up one more.

AllTerrainX · October 12, 2016

manual mode is range mode.

ie. if in 2nd will use 1 & 2. If in 5 will use 1-5.

the manual has more info

Here are some screenshots attached from the online manual. Now I know what Range Selection Mode is but doesn't mention anything about AFM / V4 mode. I am glad I found that V4 mode never engages when I don't hit the highest gear (8th)

1300c · October 12, 2016

So before you started driving in m7 you mentioned the exhaust sound wasn't good with your gm performance exhaust. Did you notice the drone/helicopter sound people complain about when not using the flapper in the stock exhaust? Thank you!

AllTerrainX · October 12, 2016

So before you started driving in m7 you mentioned the exhaust sound wasn't good with your gm performance exhaust. Did you notice the drone/helicopter sound people complain about when not using the flapper in the stock exhaust? Thank you!

I have looked at my All Terrain performance exhaust and have never noticed a "flapper". I have read about it on these forums that its after the muffler? Might have to take a look tomorrow. And yes when it switches from V4 to V8, it would make this weird rumble/bogging, guess you could say its a helicopter sound, from the exhaust. It worried me sometimes cause it didn't sound normal to me, especially for a brand new truck.

DAP56 · October 12, 2016

I drive in M7 exclusively. I hate the AFM and won't tolerate the sound or spudder while in D. I got the idea from the M5 guys with the 6 speed. OP is correct, there hasn't been many posts about M7 as the 8 speed was offered on late 2015 and newer models. I too am thinking Black Bear at some point.

Sent from my iPhone using Tapatalk

1300c · October 12, 2016

I have looked at my All Terrain performance exhaust and have never noticed a "flapper". I have read about it on these forums that its after the muffler? Might have to take a look tomorrow. And yes when it switches from V4 to V8, it would make this weird rumble/bogging, guess you could say its a helicopter sound, from the exhaust. It worried me sometimes cause it didn't sound normal to me, especially for a brand new truck.

On the stock exhaust systems it's directly behind the muffler. On the GM Borla exhaust it's in front of the muffler. I was wondering if the sound was noticeable on the GM corsa exhaust (which is what you have) if the v4 done was noticeable. Thank you for answering my question!

AllTerrainX · October 12, 2016

On the stock exhaust systems it's directly behind the muffler. On the GM Borla exhaust it's in front of the muffler. I was wondering if the sound was noticeable on the GM corsa exhaust (which is what you have) if the v4 done was noticeable. Thank you for answering my question!

I kinda went under my truck this morning and looked at the exhaust, before and after the muffler and still didn't see a flapper. I will have to really get under there this weekend to take a better look. Maybe take some pictures.