Disable AFM

[AWSMBLU]

https://gmauthority.com/blog/2025/02/little-known-chevy-silverado-tahoe-suburban-trick-disables-dfm/

 

[Joseph Garcia]

Interesting. Who knew? Could be a good way to temporarily eliminate DFM functionality, while waiting or preparing physical work for its complete elimination.

 

[AWSMBLU]

Interesting. Who knew? Could be a good way to temporarily eliminate DFM functionality, while waiting or preparing physical work for its complete elimination.

It also disabled the start stop

 

[DontTaseMeBro]

Interesting. Who knew? Could be a good way to temporarily eliminate DFM functionality, while waiting or preparing physical work for its complete elimination.

Joe, it’s been well documented across multiple threads in this sub-forum.

Take this one for example:

Driving in L9 and DFM

Greetings all Has anyone confirmed if driving in L9 will disable DFM? I haven't been able to find anything on the forums and haven't noticed whether it works or not . I have tried it but can not confirm for sure seeing that there is no indicator stating such. Plenty of older trucks that do...

www.tahoeyukonforum.com

 

[Joseph Garcia]

Joe, it’s been well documented across multiple threads in this sub-forum.

Take this one for example:

Driving in L9 and DFM

Greetings all Has anyone confirmed if driving in L9 will disable DFM? I haven't been able to find anything on the forums and haven't noticed whether it works or not . I have tried it but can not confirm for sure seeing that there is no indicator stating such. Plenty of older trucks that do...

www.tahoeyukonforum.com

It was news to me, so it may be news to others. I don't know all of the answers, and I look forward to learning something new every day.

 

[RG23RST]

Yes that's been a thing even going back to the 6 speed units a decade ago.

It "shouldn't" hurt anything but at the same time I'm not sure I would guinea pig myself for 100K miles running on the highway in 9th gear with the E clutch applied. Probably a non-issue though.

 

[swathdiver]

Yep same as running in M5 with the 6-speeds.

Well, the EPA will no longer enforce the Clean Air Act and GM and the others will likely get rid of AFM from new production engines soon enough.

 

[PPV_2018]

Yep same as running in M5 with the 6-speeds.

Well, the EPA will no longer enforce the Clean Air Act and GM and the others will likely get rid of AFM from new production engines soon enough.

Yeah i wouldn’t count on that. I can’t see gm deleting afm from future production considering the possibility of the next U.S. administration reinstating tighter emissions rules. That would cost gm lotsa “zeros” whereas it would be cheaper for them just to keep this already established “technology” under the guise of saving you, the consumer, money on fuel.



At any rate, this thread should be a sticky, for those who are unaware.

 

[swathdiver]

Yeah i wouldn’t count on that. I can’t see gm deleting afm from future production considering the possibility of the next U.S. administration reinstating tighter emissions rules. That would cost gm lotsa “zeros” whereas it would be cheaper for them just to keep this already established “technology” under the guise of saving you, the consumer, money on fuel.



At any rate, this thread should be a sticky, for those who are unaware.

Or they could delete it and offer vehicles for less money while increasing their profits. We shall see.

 

[RG23RST]

N

Yep same as running in M5 with the 6-speeds.

Well, the EPA will no longer enforce the Clean Air Act and GM and the others will likely get rid of AFM from new production engines soon enough.

Not how that works. CAA is Congressional legislation and isn't going anywhere. GM gets the 5.3 to ULEV50 with DFM and they sell that engine in other markets so there's no point in having multiple versions. Whichever way GM wants to meet the law is up to them. Big gov doesn't require cylinder deactivation but it helps meet the target. Ford went the opposite route for their volume engines (2.7 and 3.5) with smaller displacement and sell relatively few V8s now even though those have cylinder deactivation too.

What little has trickled down to us concerning the new engines for 27/28 indicates they'll still employ the deactivation technology along with cooled EGR which has been on the Ford stuff for a few years now. That's secondhand information from the bosses that attend dealer shows so take it for what it's worth.

 

[Stewmatic]

We paid all this money for the vehicles and worry about the engine and transmission all the time. It’s really a shame. I haven’t had any issues with mine. But man it’s scary to read. I am out of warranty soon.

 

[swathdiver]

N

Not how that works. CAA is Congressional legislation and isn't going anywhere. GM gets the 5.3 to ULEV50 with DFM and they sell that engine in other markets so there's no point in having multiple versions. Whichever way GM wants to meet the law is up to them. Big gov doesn't require cylinder deactivation but it helps meet the target. Ford went the opposite route for their volume engines (2.7 and 3.5) with smaller displacement and sell relatively few V8s now even though those have cylinder deactivation too.

What little has trickled down to us concerning the new engines for 27/28 indicates they'll still employ the deactivation technology along with cooled EGR which has been on the Ford stuff for a few years now. That's secondhand information from the bosses that attend dealer shows so take it for what it's worth.

It's kinda early to tell. However the EPA is saying that they cannot enforce it and are kicking enforcement over to the DOJ it seems. I think Ford was foolish for making those engines but after seeing how they engineer stuff over the last 25-30 years, well, it just reinforces my opinion and will probably never own one again.

 

[RG23RST]

It's kinda early to tell. However the EPA is saying that they cannot enforce it and are kicking enforcement over to the DOJ it seems. I think Ford was foolish for making those engines but after seeing how they engineer stuff over the last 25-30 years, well, it just reinforces my opinion and will probably never own one again.

Again, that’s not how that works. NAAQS are legislatively mandated by the Clean Air Act and subsequent revisions. Statute of limitations for CAA knowing violations is 5 years so no business operating above board is going run the risk of violating the law.

 

[WalleyeMikeIII]

Plus, it is entirely unclear whether "disabling" (a better description would be preventing the entry and exit of cylinder deactivation; leaving all cylinders enabled at all times) really enhances durability or not. The weak point is the needle bearing in the lifter...and it isn't clear preventing lifter collapse or not really mitigates that. So, aside from maybe maintaining the thermal consistency across the block (which I think is handled by DFM by design), simply preventing the entry/exit of deactivated cylinders, when all the known failing components are still present, probably does little other than a placebo affect for the owner?

 

[swathdiver]

Again, that’s not how that works. NAAQS are legislatively mandated by the Clean Air Act and subsequent revisions. Statute of limitations for CAA knowing violations is 5 years so no business operating above board is going run the risk of violating the law.

Ok, starting to get some of what you're putting down. On a slightly different topic, what about the CAFE standards being eliminated? Wouldn't that allow GM and the others to dump AFM since that system is not directly tied to emissions standards?

Which makes me ask, are there specific emissions standards for vehicles specified in the CAA? Or does the CAA tell the government to figure it out?

 

[RG23RST]

Ok, starting to get some of what you're putting down. On a slightly different topic, what about the CAFE standards being eliminated? Wouldn't that allow GM and the others to dump AFM since that system is not directly tied to emissions standards?

Which makes me ask, are there specific emissions standards for vehicles specified in the CAA? Or does the CAA tell the government to figure it out?

Your 2nd paragraph requires an answer too long to type at the moment.

CAFE is not a bad idea just implemented poorly largely because of the revolving door between big business and government. Larger vehicles are more profitable and CAFE essentially pulled forward a lot of demand in larger vehicles over the years. Had it been written fairly we’d still have more choice in smaller vehicles. Tangent to that we almost got a new national fuel standard post 2008 crisis. Not only would it be cheaper to have only 1 grade of fuel produced and transported it would help automakers to meet mpg and emissions targets. Sadly the oil companies nixed that in the name of profit. IIRC there was a serious proposal to standardize on 91 octane E10 with some exceptions for places like Southern California, Atlanta etc where smog is a problem.

 

[swathdiver]

CAFE is not a bad idea just implemented poorly...

CAFE forced the automakers to produce little cars nobody wanted. Then they focused on what we did want, big cars and later trucks. Then they imposed those standards on the trucks. At one point the government considered my Yukon XL as getting 59 mpg because it was FlexFuel. The other regulations basically forced the cars to disappear or become massively heavy. My 1980s G-Body cars had a curb weight of around 3200 pounds, while these new Dodge Challengers weigh 4,400 pounds.

Well, these government agencies will not make law with their rules and regulations anymore, that's supposed to go back to Congress. Hopefully, they follow through with it.

 

[RG23RST]

CAFE forced the automakers to produce little cars nobody wanted. Then they focused on what we did want, big cars and later trucks. Then they imposed those standards on the trucks. At one point the government considered my Yukon XL as getting 59 mpg because it was FlexFuel. The other regulations basically forced the cars to disappear or become massively heavy. My 1980s G-Body cars had a curb weight of around 3200 pounds, while these new Dodge Challengers weigh 4,400 pounds.

Well, these government agencies will not make law with their rules and regulations anymore, that's supposed to go back to Congress. Hopefully, they follow through with it.

CAFE did not "force" auto makers to do any such thing. It's a mischaracterization of the Standards to say that. American OEMs simply did not invest in those products like the foreign brands. There is no disagreement that these Standards have made modern vehicles a "modern marvel" in their power and relatively clean emissions. An L87 emits something like 90% fewer greenhouse gas emissions than a small block from the mid 80s.

If a lack of regulations is more to your liking, there are numerous "third world" countries to choose from to be free from such regulations as airbags, crumple zones and intrusion protection. That'll get you those light cars you like so much. Thankfully Congress has already "made the law" decades ago and continued to amend it as necessary. I can assure you the phrase "the Secretary shall prescribe...." is going nowhere from the Federal Register and will continue to carry the full weight of civil penalties for noncompliance. Loper Bright Enterprises v. Raimondo only dealt with "ambiguous" language. All it does is shift the balance of refereeing disputes slightly away from defaulting to the agency interpretation. I say slightly because in the interim between the 1980s and now, Congress amended the CAA to plug the holes Reagan's EPA used to favor polluting industries.

 

[swathdiver]

CAFE did not "force" auto makers to do any such thing. It's a mischaracterization of the Standards to say that. American OEMs simply did not invest in those products like the foreign brands. There is no disagreement that these Standards have made modern vehicles a "modern marvel" in their power and relatively clean emissions. An L87 emits something like 90% fewer greenhouse gas emissions than a small block from the mid 80s.

If a lack of regulations is more to your liking, there are numerous "third world" countries to choose from to be free from such regulations as airbags, crumple zones and intrusion protection. That'll get you those light cars you like so much. Thankfully Congress has already "made the law" decades ago and continued to amend it as necessary. I can assure you the phrase "the Secretary shall prescribe...." is going nowhere from the Federal Register and will continue to carry the full weight of civil penalties for noncompliance. Loper Bright Enterprises v. Raimondo only dealt with "ambiguous" language. All it does is shift the balance of refereeing disputes slightly away from defaulting to the agency interpretation. I say slightly because in the interim between the 1980s and now, Congress amended the CAA to plug the holes Reagan's EPA used to favor polluting industries.

I disagree, the automakers said it themselves over the years.

No, I prefer to be able to choose and pay for those features or not. I have no need of a statist thousands of miles away thinking they know better how to direct my path through life.

To your other point, I believe it was recently said that the current emissions standards are no better in curbing pollution from automobiles than what we had in the 1990s. I've been loosely poking around to find some data on that subject, maybe you know?

 

[swathdiver]

At one point the government considered my Yukon XL as getting 59 mpg because it was FlexFuel.

I want to correct this statement. Under CAFE standards, the government assigned an Average E85 MPG value of 80 miles per gallon to the 2007-2009 Suburban/Yukon XL. Using the average mileage on gasoline of 16 MPG, they were assigned a CAFE MPG rating of 26.7 Miles Per Gallon.

The more popular 2010-2014 GMT900 SUVs with the 5.3 were assigned an Average E85 MPG value of 87 miles per gallon.

These are the two formulas:

Average CAFE E85 MPG = Average E85 MPG/.15

CAFE MPG Rating = 1/(0.5/Average Gasoline MPG+0.5/AVERAGE CAFE E85 MPG)

They use the Average Fuel Economy of both fuels, gasoline and E85 and apply a conversion factor to E85 to boost the mileage for CAFE. This is of course incentivized the automakers to produce FlexFuel vehicles and add other fuel saving features to their engines or pay a fine of $5 for every tenth of a mpg below the standard, per vehicle.

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://info.ornl.gov/sites/publications/files/Pub37730.pdf

35.5-mpg CAFE Explained

More details are coming to light on the coming Corporate Average Fuel Economy and Greenhouse Gas requirements, and many of these details make the 35.5-mpg target a bit less daunting. Find out more about the new CAFE regulations in this feature from the automotive experts at Motor Trend.

www.motortrend.com

MOPAR is gearing up to stick a 426 under the hood everything it has and Ford was recently seen in the wild testing deleted 6.7s for public consumption, not government.

HR4117 is due to pass this month cementing these and other automotive changes we talked about earlier into place.