2012 LT. Does this motor have the 8 to 4 cylinder problem that the range device addresses? Just bought it today.

[S1W99]

 

[wsteele]

Nice truck, congrats.

The 8 to 4 cylinder "problem" is called AFM (Active Fuel Management) and yes, your truck has it. In the later models like yours (nit so in my 2007 Yukon), they made a lot of upgrades to the AFM components and some related issues, such that these models are more reliable in that department than earlier versions. That upgraded reliability is contingent on regular maintenance.

I think most on here would recommend turning AFM off. The Range device can do that, but to my mind is not the optimal way to accomplish it. The Range device uses the ODB port, such that if you have to access that port, you must remove the range device to use it and in doing, re-enable the 8 to 4 equipment, perhaps after sitting idle for an extended period of time. There are less expensive ways to turn AFM off ($50 ECM reflash) and more expensive and elegant approaches as well.

In the end, turning AFM off is quite easy and probably a good idea in the long run, albeit less urgent in a later model like yours.

 

[S1W99]

Nice truck, congrats.

The 8 to 4 cylinder "problem" is called AFM (Active Fuel Management) and yes, your truck has it. In the later models like yours (nit so in my 2007 Yukon), they made a lot of upgrades to the AFM components and some related issues, such that these models are more reliable in that department than earlier versions. That upgraded reliability is contingent on regular maintenance.

I think most on here would recommend turning AFM off. The Range device can do that, but to my mind is not the optimal way to accomplish it. The Range device uses the ODB port, such that if you have to access that port, you must remove the range device to use it and in doing, re-enable the 8 to 4 equipment, perhaps after sitting idle for an extended period of time. There are less expensive ways to turn AFM off ($50 ECM reflash) and more expensive and elegant approaches as well.

In the end, turning AFM off is quite easy and probably a good idea in the long run, albeit less urgent in a later model like yours.

Thank you for such a detailed reply. I'm selling an '07 that needed the range device. I was hoping I could not use anything while on a long highway drive for better mileage. I have no issues now.

Is it a good idea to get the issue fixed with a flash even if you're not having problems or wait until you start to feel the shutters?

 

[swathdiver]

Thank you for such a detailed reply. I'm selling an '07 that needed the range device. I was hoping I could not use anything while on a long highway drive for better mileage. I have no issues now.

Is it a good idea to get the issue fixed with a flash even if you're not having problems or wait until you start to feel the shutters?

Change the oil every 5K miles and leave it be. How many miles are on it? A fairly high percentage of all years had to have their AFM systems rebuilt, an even larger percentage went their entire lives, 200K+ miles without fail.

 

[S1W99]

148K no issues.

 

[wsteele]

Thank you for such a detailed reply. I'm selling an '07 that needed the range device. I was hoping I could not use anything while on a long highway drive for better mileage. I have no issues now.

Is it a good idea to get the issue fixed with a flash even if you're not having problems or wait until you start to feel the shutters?

The unfortunate thing is nobody can answer your question with factual data, it is only going to be opinions, some stronger felt than others.

As far as waiting to do something before getting a range device or shutting AFM off in the software, at that point it likely is too late to avoid some fairly costly repairs, pulling heads, replacing lifters, perhaps replacing the cam and at that point "while you are in there" replacing the oil pump, etc. etc. etc.

On the other hand, as Swathdiver points out, a large percentage of these trucks run their whole life without any AFM problems cropping up (especially the later models like the '12's). The most frequent occurrences of problems seem to happen with trucks that have been neglected, particularly in and around the oil change interval. The most experienced members I have read on these forums contend there is nothing more important than regular oil/filter changes (like every 5K, one very experienced member here changes his every 3K miles).

The best approach to turning off the AFM function is also a little more nuanced than what the "bigger hammer" crowd might contend. If you live in California and are in a county that requires regular smog checks (emissions tests), with recent changes to their way of checking for compliance, you might only have the Range device as an option to turn it off, as some have posted CA is now able to check the software in your engine management and determine if it has been modified.

In addition, if you take your truck to a dealer for service and you have used the PCM reflash approach to turn AFM off, it can be undone unsuspectingly by the dealer service guys if they download a new revision for you and flash your PCM. If you do your own work, or have a reliable independent shop do your work, this exposure is less because they likely wouldn't be downloading new revisions.

My '07 has similar mileage on it as yours and I elected to turn off AFM in the software (I used a Diablo Predator device to do it, in retrospect just about the worst way you can choose in my opinion, but that in itself is its own thread... ). I still run the risk of the dealer refashing my PCM for some unrelated reason while it is in the shop, but at the age of my truck and the revision status it is at (my PCM has all the current GM revisions in it and they likely aren't going to be issuing many mandatory new ones), that chance is pretty small.

Anyway, I think if the maintenance status has been really good on your truck, you probably have time to ponder and read up on AFM and get that doctorate in internet opinions on the subject.

Good luck.

 

[S1W99]

The unfortunate thing is nobody can answer your question with factual data, it is only going to be opinions, some stronger felt than others.

As far as waiting to do something before getting a range device or shutting AFM off in the software, at that point it likely is too late to avoid some fairly costly repairs, pulling heads, replacing lifters, perhaps replacing the cam and at that point "while you are in there" replacing the oil pump, etc. etc. etc.

On the other hand, as Swathdiver points out, a large percentage of these trucks run their whole life without any AFM problems cropping up (especially the later models like the '12's). The most frequent occurrences of problems seem to happen with trucks that have been neglected, particularly in and around the oil change interval. The most experienced members I have read on these forums contend there is nothing more important than regular oil/filter changes (like every 5K, one very experienced member here changes his every 3K miles).

The best approach to turning off the AFM function is also a little more nuanced than what the "bigger hammer" crowd might contend. If you live in California and are in a county that requires regular smog checks (emissions tests), with recent changes to their way of checking for compliance, you might only have the Range device as an option to turn it off, as some have posted CA is now able to check the software in your engine management and determine if it has been modified.

In addition, if you take your truck to a dealer for service and you have used the PCM reflash approach to turn AFM off, it can be undone unsuspectingly by the dealer service guys if they download a new revision for you and flash your PCM. If you do your own work, or have a reliable independent shop do your work, this exposure is less because they likely wouldn't be downloading new revisions.

My '07 has similar mileage on it as yours and I elected to turn off AFM in the software (I used a Diablo Predator device to do it, in retrospect just about the worst way you can choose in my opinion, but that in itself is its own thread... ). I still run the risk of the dealer refashing my PCM for some unrelated reason while it is in the shop, but at the age of my truck and the revision status it is at (my PCM has all the current GM revisions in it and they likely aren't going to be issuing many mandatory new ones), that chance is pretty small.

Anyway, I think if the maintenance status has been really good on your truck, you probably have time to ponder and read up on AFM and get that doctorate in internet opinions on the subject.

Good luck.

Thank you sir I really appreciate the input.

 

[iamdub]

IMO, I'd disable it due to the simple fact that the system doesn't return enough MPG to outweigh the risk.

Your '12 should have the latest iterations of the VLOM and lifters, making your AFM system the most reliable version. However, it's still a risk. Calculate your price of fuel and current average MPG to determine your cost per mile in cents. Do the same calculations assuming 2 MPG less and see the difference in cost per mile. It'll be pennies. Now, calculate how many pennies it'll cost should a lifter fail and need replacing. At best, one lifter (although you should replace all on the bank you open up), a head gasket, maybe intake manifold gasket set, fluids, labor if you pay for it, etc. Now, calculate how many miles you drive on average to see how long you'd have to drive achieving that 2 MPG better economy to just break even with the cost of repair.

Or, for ~$60, have it turned off and keep clean oil in the engine and never give it a second thought unless it starts to makes noise.

 

[S1W99]

It's as simple as you made it. It'll never be worth the risk.

So where do I get the $60 option you mentioned? Instead of the range device that's $200.

 

[iamdub]

It's as simple as you made it. It'll never be worth the risk.

So where do I get the $60 option you mentioned? Instead of the range device that's $200.

Here:

AFM Delete

It's $50 plus whatever it costs you to send them your PCM. Return shipping from them is included in the $50.

BTW, I don't mean to bash GM for their AFM. They tried and are continuing to improve their product because they have to due to the ever-tightening EPA standards. You've heard of the old adage "Never buy a first year model". '07-'09ish is the "first year model" of GM's AFM system. You have the second (or third?) "model", which is a nice improvement, but still. I gave mine plenty of testing before disabling it. Now, with a mild cam, mild head work and all the other mods in my sig, I meet and often exceed the stock-with-AFM fuel economy. I'm also about 80 horses stronger, and that estimate might be a little conservative.

Also, I'm not bashing the Range- it has its place. But, if your locale requires annual emission inspections, you'll have to unplug the Range. First off, you'll be reawakening a system that's been hibernating for a year. This makes me nervous. Secondly, unplugging it resets readiness monitors so you'll have to complete certain drive cycles before you can take it in for inspection. Depending on many factors (not just driving X number of miles), this could be a few days to a couple of weeks. Thirdly, there have been reports, at least with the older versions of the Range, of it draining the car's battery if it sits parked for extended periods. So, you'll have to remember to unplug it if this applies to you.