How AFM Works
| | | | | | | |

How to Delete or Disable Active Fuel Management (AFM)

Jake Mayock

Meet Jake

Jake is a founder of 8020 Media and has been creating automotive content online since 2017. He has been the lead writer for Chevy Trucks and has transformed it from the old and outdated site it was into what it is today. Jake creates a ton of GM related content for the 8020 Media YouTube channel and specializes in Duramax and Vortec information but has a wealth of knowledge across all GM cars and engines. Jake believes the L5P is the best diesel on the market today.

AFM or active fuel management is a GM/Chevy technology meant to improve gas mileage. AFM works by deactivating half of the engines cylinders under certain circumstances to reduce fuel usage. It essentially turns your V8 engine into a V4 which saves fuel.

GM claims fuel improvements ranging from 5%-15% depending on the engine. So why would you want to delete AFM? Unfortunately, it causes a number of issues for the Vortec and EcoTec3 engine family. Engines that are equipped with AFM are known to have lifter failure, oil life monitoring system issues, and excessive oil consumption.

The excessive oil consumption caused by active fuel management combined with defective oil monitoring systems has caused numerous owners to experience premature catastrophic engine failure.

To prevent any engine problems caused by AFM you can either delete or disable the system.

How AFM Works

What Engines Have AFM?

AFM is equipped on various Vortec engines. However, you need to look into your specific engine code as AFM is not used in every single engine.

How Does it Work?

The top of the cylinder block has a valley cover over it which is called the lifter oil manifold assembly (LOMA). All Gen IV Vortec engine blocks have AFM towers and oil passages built into them. On non-AFM vehicles, the valley cover is completely flat and the towers and oil passages aren’t used. AFM vehicles come equipped with a special valley cover that has solenoids, oil pressure senders, and electrical connectors in it.

Additionally, the lifters on AFM engines are different. Cylinders 1, 4, 6, and 7 have taller lifters with oil holes in them. These are the cylinders that will shut off when AFM is activated.

When engine load is low AFM is activated. When this happens the GM ECU sends a signal to the valley cover which then opens the solenoids. Oil then flows to the lifters with the oil holes which causes the plunger inside of the lifter to close. When the plunger closes the lifters collapse and therefore do touch the pushrods which keeps both the intake and exhaust valves closed.

When load increases the valley cover solenoids close cutting oil off from the lifters. As the existing oil in the lifters funnels out they begin to function properly again re-engaging all 8 cylinders.

Understanding how active fuel management works is important for understanding how to delete it.

Preventing Problems: Delete or Disable It

The primary benefit of deleting or disabling active fuel management is in preventing engine problems. However, there are a few additional benefits. First of all, the V8 power is always available when you need or want it. And secondly, your Chevy will sound like a V8 and not like a little V4 Honda.

  • Reduced likelihood of lifter failure
  • Stops excessive oil consumption
  • Louder exhaust notes
  • V8 power is always there when it’s needed

There are two options to fix the AFM issues on Vortec engines.

Option 1: disable the AFM system. Disabling AFM simply adjusts the engines ECU so that it never activates AFM. It essentially prevents the valley cover solenoids from ever opening.

Option 2: completely delete it. Deleting the AFM system requires replacing all of these special parts with standard non-AFM parts. As you can imagine, this requires a good bit of labor and is also quite a bit more expensive.

How to Disable Chevy AFM

Disabling active fuel management requires either reprogramming or tricking the ECU into staying in V8 mode. To do so, you will need an AFM Disabler device. This device simply plugs directly into the OBDII port and starts working immediately. If you ever want to turn it back on or don’t want to take it to the dealer with AFM disabled, simply remove the device.

We recommend the Range Technology disabler since it is the only device on the market that doesn’t reprogram your ECU. Reprogramming the ECU voids engine warranty which is why this option is the best for anyone who still has some factory warranty left. The Range device comes in a few different colors, the different colors mean nothing. They do light up and are noticeable under the dash so they provide a few options for people who want different colors illuminating from their footwells. If you find the colors annoying you can simply put some tape over the LEDs.

Recommended Disabler: Range Technology AFM Disabler

How to Delete AFM

Deleting AFM is a bit more of a pain since it requires replacement of all of the components. We generally only recommend deleting the system if you have failed lifters and have to do all of the labor anyways to replace them. Deleting the system also requires you using a disabler device or a custom tune so again, only do this if you really have to.

Here is a short checklist of what needs to be done to completely delete active fuel management:

  • Replace your camshaft with a non-AFM camshaft
  • Swap out the AFM lifters for standard lifters
  • Replace the valley cover with a flat, non-AFM valley cover
  • Disable the AMF system with the Range Technology Disabler, or custom tune it out
  • Plug the pressure relief valve in the oil pan
  • Swap the high-volume oil pump for a standard oil pump

A few random notes to go along with this as well. If you want to use a disabler instead of a programmer to turn AFM off then you need to leave the solenoid wires connected. If you do this, you can keep the AFM valley cover as well which will reduce some costs compared to replacing it.

Which Option is Better?

Unless you have failed lifters we recommend disabling AFM. Deleting it requires replacing a lot of parts, gaskets, etc. which makes it more expensive parts wise, but also requires a lot of labor which is expensive you aren’t DIY’ing the project.

Additionally, disabling it allows you to turn it back on whenever you want. This lets you maintain your factory warranty and allows you to reinstall it if anything goes wrong from it being disabled.

If you do have failed lifters you can simply replace the lifters and then install a disabling device. The only reason we mention deleting it is that it doesn’t require a whole lot of extra labor to do so if you have to replace the lifters anyways.

Summary

AFM lifters are known to fail more frequently than non-AFM lifters. Additionally, the system leads to excessive oil consumption. The excessive oil consumption can lead to oil levels running low, pressure dropping, and various major components such as the timing chain failing. Overall, the AFM system is responsible for a lot of very expensive repairs.

To prevent spending big money on AFM related repairs, the best option is to simply delete or disable the system. Not only is it a good thing to do for preventative maintenance, it also gives you a better exhaust sound and keeps your car in V8/V6 mode at all times.

Disabling the system is the best way to go as it is the cheapest option and keeps any factory warranty.

Have you had any issues with your AFM system? Let us know in the comments and whether or not you went for a disable or delete kit.

Similar Posts

60 Comments

  1. I have a 2011 Chevy 1500 5.3 4×4 the AFM very rarely engages snd when it does it only engages for a couple seconds snd then straight back into v& mode it’s actually making me use more gas and I’m using about 21/2 -3 quarts of oil between changes I was getting 18.5 mpg average it has dropped to 13.5 mpg I have changed plugs wires air filter but can’t get mileage back up and truck seems sluggish and just doesn’t have the power it did have. I can turn the stabilatrac off and it sounds and feels like a completely different truck but the next time I turn it off it doesn’t do anything and it has more power with it on it also when I turn it off the low end ain’t worth a flip but the midrange runs awesome don’t seem to have much power low end some times when it’s turned off but either on or off my mileage does not get better any help in this matter would be greatly appreciated

  2. Great helpful information i have a 2012 and a 5.3 V8 in my Silverado……I’m going to have my FMS shut off by a shop that can do it for $175.00 I’m not going to do the ALD plug in for a around $110.00…I also have that slight flutter at highway speeds But only for a few seconds as it switches between a V4 and a V8…But my power low and mid range seems ok.

  3. I recently completely deleted the AFM system in 2013 Avl, installed new lifters. Springs, stage 2 cam, tuned on dyno & it’s pulling 282 HP to the wheels. It runs great, I Love it. Haven’t checked mileage yet.

      1. If you have emissions testing I g your area when they check it the engine rpm’s are raised anyway which puts it into V-8 mode just be sure you engine is well tuned , fuel filter changed and new air filter so the engine is getting clean air into the engine and the emissions should be in the pass range.

  4. I had completely deleted AFM system on 2008 chevrolet avalanche 5.3 everything new but when I start it up it crank and kill

    1. That’s because you have to turn arm off in the ecm and it has to be retuned for the engine and transmission

      1. I owned a 2016 6 cylinder and it ran perfectly for 170k. Sold it for good money and purchased a 2021 with 5.3 that was a victim of the chip shortage and does not have cylinder deactivation from the factory. I hope you know what your talking about because my old 6 cylinder got up to 31 mpg and a cruse range of 600 miles. My v8 cannot come close .

  5. I just disabled my afm in my 2011 Silverado when I bought it with 72,000 miles. I never replaced oil pump with a regular one, truck has 126,000 miles with zero issues.

  6. 2013 Chevy 1500 5.3. Can hear and feel when AFM kicks in and fairly certain its not acting properly. Kicks on way to soon and I feel only killing one cyl when it does. goes away when I accel. No missfires show on scanner. now to decide which deactivate system to buy

  7. I have a 2018 Silverado High Country with the 5.3 ltr. It has only 47k miles on it. One day I noticed a ticking noise. I knew right away it was a failed lifter. I have a life time warranty thru the dealer. So I took it in and that’s in fact what it was along with a bent push rod. They replaced all the lifters on the right side, replaced the bent push rod and the VLOM (which was on backorder for 5 weeks). Now it runs like a champ. So I think the only way to turn off the AFM is to put it in low gear and upshift to gear level 7. So my question is, is it better to turn off the AFM especially during city driving, or leave it in D? On the interstate, if I have the AFM turned off, my RPMs go from 1500 to 2000 at 70 mph.

    1. So eliminas el afm con un kit de cambio de árbol de levas que pasa con el cheking y el plug de afm

  8. I owned a transmission shop for 35 years before I retired and was well aware of what AFM was doing to the engines and transmissions. In 2011 my partner and I purchased two new half ton Silverado’s and in 2021 with only 62k my converter clutch started to slip on hills causing a surging sensation. I had disabled AFM at about 58k but to late and that was a $4200 repair for the internal transmission updates including a transgo shift kit, converter updated clutch valve, a new 3rd clutch drum, (they crack) and a reman converter and a back half of the transfer case housing, (corroded and cracked in front of the rear output seal). The truck also took a new fuel pump the week before due to a rust hole and evap leak on it’s housing. My Range Technology disabler is installed 24-7 and should extend the life of the engine and transmission at this point however the salt used by the Ct dot will ruin any vehicle and they don’t care. One last comment, my neighbors Saab 9-7X just lost cylinder #4 last week due to lifter failure at 150k, yes it’s a 5.3 GM Engine.

  9. I have a 2012 Suburban w/ a 5.3 and after changing the oil & filter, I now have a fairly loud lifter tick coming from #1 or #2 cylinder.
    I was thinking that I need to do a crankcase cleanout, but now I’m wondering if I should do a AFM bypass instead?
    About 177K currently – bought it used at 160K.

  10. 2015 Chevy 5.3 pickup. 85000 klm about 50000 miles on it. Noticed a ticking sound occasionally. I was in the USA took it to a dealer and they quoted me $4400.00 to fix this. I researched on line and bought a AFM disabler plugged it in . No problems so far. Don’t put a lot of miles on the truck yearly. Hoping to keep it for another year or two .

  11. I currently have a 2017 GMC Sierra 1500 4.3 LV3 with AFM lifter failure that damaged the block. So I am trying to put the LV1 engine from a 2018 GMC Savanna 2500 with the 4.3 non AFM.
    But not too much info on the swap. I think it should just bolt up and add a tuner correct?
    Any info will be appreciated.
    Thanks.

  12. I currently have a problem with my 2013 Yukon. It looks like I’m going to have a huge expense in fixing my vehicle. Is there any chance that this could be considered in a recall? My Yukon has low miles but had I known this could be an issue, I wouldn’t have bought it.

    1. Robin – unfortunately there aren’t any recalls here. What problems are you experiencing?

  13. Have a 2007 Tahoe and as I am coming to a stop the truck stutters. Have had transmission replaces 2 times. This seems to be the cause. What causes this stutter?

    1. Try adding 3oz mos2 t oil additive to Trans. Oil. If this doesn’t help after several days add 3 more oz-repeat etc

  14. Have just had transmission rebuilt. Transmission mechanic feels the stutter is the AFM System. Bought used and 3 months after had transmission replaced. Just had that one rebuilt. Added torque converter & cooling system. 210,000 miles. Want this to last me a few more years. Sounds like the range disabled is the way to go???

    1. Dave – a disabler is the way to go for sure. Most on the market will work just fine, Range is just the primary name brand.

      1. Jake Just bought a 2019 suburban 5 . 3 with 6500 mile i live fort Erie Canada enquired at two gm dealers to delete the management system they would not Doug at amish1945@hotmail.com leaving for Zephyrhills Florida on march 5 th any advice Thanks Doug

      2. Jake – do you know if leaving the solenoids connected on a DFM delete will also allow you to use a disabler, as stated with the AFM?

        I have a 2019 L84 that is 123 miles out of warranty with lifter failure (yes, GM gave me the finger). I need to do a lifter replacement, but looking for a more economical way around reprogramming the modern ecm. If the DFM solenoids can remain in and wired, this would solve a lot of issues. Just don’t know for sure.

  15. I have a 2013 Tahoe with 72,000 miles. I have installed a AFM disabler. Am I still at risk for engine failure? Would you recommend I sell it soon?

    1. Hey Karolyn – this should solve any issues with premature failure caused by the AFM system. It’s of course not an absolute guarantee, but I wouldn’t be concerned enough about reliability to consider selling it.

  16. so this system mentioned to “disable”, will its tricking the ecu trigger an CEL?

    i pulled the fuse thinking it a solution and it was until a code was given.

    im going to check out this system mentioned.

  17. Great write up!!

    I have a 2009 Silverado that I will be performing the physical delete on. Standard lifters, new valley cover, plugging the oil pressure valve on the pan, standard non DOD cam. My question is regarding the post swap tune.

    I will be performing the work with my brother in Austin TX, and I know this was mentioned in the article but is it possible to simply install the range afm device as a temp while I drive back home to Hays, KS, after which I will use TSP’s mail order tuner service to permanently time it out? Thanks for all the great info and for taking my question!

    1. Juan – absolutely, the Range device is purely plug-and-play just unplug it and the truck won’t ever know it was even on there.

    2. “Post swap”, I’m under the impression that the ECM won’t detect the AFM solenoids in the valley plate, and the ECM will disable fuel to the 4 cylinders. This would be a problem till the ECM was tuned for the deleted valley plate.

  18. I have 2020 1500 lt crew cab with an infotainment system failure. I tried fixing this myself as the damage was self inflicted. On the back of the system there are two connectors going to the LED screen one of which has 2 wires going to it (the connector has 8 pins only two are used). I need to know which two pins these wires go to. It’s either a pin on each side, meaning 1 and 8 or it’s one pin in meaning 2 and 7. I cut the connection now I have to make a new connection. I’ve purchased 2 infotainment systems from the dealer and they will not cover this under warranty. Possibly a new wiring harness which one do I need

  19. Hello Jake!

    I purchased a CPO 2017 Suburban LS about a year ago with ~70K on the clock..

    Over the summer the transmission gave up the ghost and it was replaced under the CPO warranty.

    Now at ~88K the vehicle was stricken with the dreaded lifter failure “dead misfire on cylinder 7” as related to the AFM and the dealer replaced the left side valve lifters.

    Fingers crossed that everything is GTG now (but if not, “please let it fail within the next year.”).

    My question is –

    Would it be prudent to purchase an AFM disabler at this point to preserve the new lifters and maybe prevent the right side lifters from failing?

    or

    Not purchase the AFM disabler so if the right side is going to fail it will fail within the next year and the CPO warranty will cover it?

    Thank you in advance!!

    Rob C.

  20. Have a 2013 Suburban 1500 z-71 4Whl drive with tow package. Have had all AFM issues in article. At 100k miles, under warranty, dealer repaired 7th cylinder/ lifter issue. Now at 247k, most likely have another lifter issue. Suburban still in very good shape otherwise, therefore will probably install an AFM Delete kit. Use the vehicle to pull 14’x7’x7’ cargo trailer. Make 2000 mile round trips from TX to MidWest ~6 times per year, 5k-7k pound loads. Article suggest changing from high volume oil pump associated with AFM system, to standard pump. With trips and loads involved, should I really go to standard volume oil pump.? Thank You!
    *PS: MPG with AFM has been historically terrible… Non-Tow: 14-15 MPG; Tow: 8-10 MPG.
    Prior two Suburbans (1994, 2003) averaged 16-18 MPG, non-tow, non-AFM.

  21. Great article.
    I have a 6.2 that the lifter stuck. I did the tap on the lifter trick and it unstuck. Can I just have the ECM reprogrammed to disable the AFM?

    1. David – absolutely, you can use a tuner like HPTuners to program it out if you don’t want to go the plug-and-play device route.

      1. Hello, I have the same problem with my 15 silverado..stuck lifter..im going to release it by tapping it..so if I just connect the Range devise..am I good also?? I hope so..this crap is getting expensive..lol

  22. I have a 2015 Tahoe 5.3L L83 it is throwing the cylinder 6 misfire code and a random miss fire. Mechanic said the solenoid failed in the lifter oil valley manifold cover. Everything is back ordered and they are not being made. Will the range disabler still work or should the delete be done.

  23. I have a eAssist 2018 Silverado. To disable AFM, I use a Range most of the time or drive in L7. I would like to install a complete AFM delete kit but so far I have not found anyone that makes one for the eAssist. This is due to the programming required.
    Has anyone heard of a AFM delete kit for eAssist 1500’s. Thank you for your time.

  24. 2018 tahoe, 130000kms, range disabler makes the truck go on beast mode.

    V4 mode feels like 1.6l corolla rolling down the hill.
    I didn’t buy a v8 to play hopscotch on v4

  25. I have a 2018c5.3 Silverado. I normally just turn off the AFm by going up to 5th gear.
    Does the “Range” device still allow the transmission to shift into 6th gear?

  26. Girl I tried to help out has a 06/07 tahoe 5.3 Had a lifter tick in #1. my Ole man an I tore the top end apart replaced the timing chain crank gear cam gear new AFM lifter kit with gaskets. Replaces valve seals in the head found several broken valve springs and replaced those. Put it all back together an it’s acts like it’s missing. Did NOT replace the cam shaft. Now im up to my neck in BS. Any advice would help.

  27. The AFM system will turn off if you drive in 5th gear. Will driving in 5th gear cause any transmission problems or any other problems ?

  28. I have a 2011 Chevy Silverado has collapse lifter I have purchased online from AMS racing the delete kit with the non DOD cam, non DOD lifters, plugged valley cover, and all the gaskets. I’m looking for someone to delete the afm out of the ECU.

  29. I have a collapsed lifter now..and I just want to release the collapse and use the range devise..is that a good idea? Just release the lifter and connect the range Disabler??? As I don’t have the extra $$ to do anything else..would that help?

  30. I think either way sounds like a win win…disabler should work..or if the other side fails within the year..the only difference will the time spent in the shop if the other side fails..rather than the Range disabler sounds like…

  31. I have a 2007 Chev Tahoe with the Vortec 5.3L and AFM. It recently started having a periodic misfire that we determined was in cylinder #4, as well as a “shudder” throughout the vehicle when coming to a stop and the engine rpm’s come down under 1000. Hoping that an AFM disable device might delay complete engine replacement. My only hesitation is it seems they all drain your battery when the vehicle is not in use. Is that the case? Are there any that won’t drain the battery when the vehicle is parked and off?

  32. I’m curious about the oil pump. Prior to doing a complete delete: lifters, valley plate, oil pan bypass valve, non AFM camshaft, M365 Melling oil pump, there were no “Low Oil Preasure” warnings. Now the 2008 Tahoe with 200,676 miles fails to maintain enough oil pressure.

    Is everyone replacing cam bearings and or using the original oil pump? What have I missed here? Any help would be greatly appreciated.

  33. Have you ever heard of this similar problem in the 2.4L Vortec? I have a 2014 Equinox and it has both idiot lights on, won’t start on random occasions and it is throwing the 0100 code (ECM) with residual codes TCM ABS etc. Yet it is absolutely random. I have disconnected the battery cables and mimicked a hard reset but still same thing? I have resoluted to replace the ECM when I can afford it but still leery because all I can afford is a refurbished one that has been completely wiped clean of any pre-programming. It’s hard being a chick 1/2 ass knowledgeable but the 1/2 I don’t know is the actual repair part and taking to a mechanic is not an option for me financially right now..anyway just thought I would pick your brain because out of all the reading and video watching (and I’ve done a lot) your advice seems to be the most thorough even if it is directed to the pick up trucks. Thanks for reading!

  34. 2017 Yukon
    Bought used with 25k miles. I did not realize it had AFM until sitting in traffic on the way home. (I didn’t notice it during the test drive). I finally found and installed the “Range Technology” disabling device but not until after we had about 50k on the vehicle. The engine is much smoother with the AFM disabled and V8 power always there.
    Now at 107k the Yuk is in the shop with a dropped lifter. I have had no other issues with the engine and only wish I had found the disabling device sooner.
    I plan to have the shop clean the intake manifold while they are in there.

  35. I have spent countless hours over the past few years researching this issue. While my evidence is anecdotal, I believe I have found some rational and cost-effective solutions to the AFM issue. This is my third GM vehicle with AFM, all Sierra 1500’s, the first with a 4 speed trans, then a 6-speed, and now the 8L90 8-speed. I have towed 4-horse trailers with each of them intermittently, but not excessively, and have never had an issue with the AFM system. My prior (two) vehicles ran to 150,000+ miles literally without any issues when I upgraded to a newer model year. All vehicles were 4WD crew cabs–the first purchased used with 20,000 miles, the second and third versions purchased new.

    My current vehicle is a 2016 Sierra 1500 AT4 (4WD crew cab) with a 5.3L and 118,000 miles. I have used the Range Technology ODB port device since 65,000 miles while searching for some solution to hard-shifting around second gear–both up-shifting (1 > 2) and down-shifting (3 >2). I have had the GM dealerships (3 different ones) check/update the software periodically to ensure it was current (to no avail) prior to the purchase and install of the Range device. I refuse to believe the “that’s the way they operate” nonsense from the service techs, as I believe the software is too damn complicated (or impossile) for anyone to fix–so they won’t fix it.

    Here are my conclusions:

    A. Change your full-synthetic engine oil and filter every 5000 miles–and never (ever!) go beyond 7500 miles–regardless of what your dash “oil life remaining” says. My research shows (again, anecdotal) that most lifter failures are due to regularly extending the oil changes beyond 7500 miles. I follow Scotty Kilmer’s recommendation that the best thing you can do to minimize engine issues is to change your oil and filter more frequently.

    B. Whenever you are towing (literally ANYTHING, be it a horse trailer, bike trailer, or a little cart to the landfill) ALWAYS USE TOW-HAUL. The 8L90 does not handle towing well to begin with, and you want to ensure it does not shift into overdrive (gears 7 and 8) when towing. Towing in overdrive will cause excessive heat, and heat is the number one killer of a transmission. Yes, the mileage per gallon will suffer driving in 6th gear, but the 8L90 is not a durable transmission–the reason why the current GM 2500 and up models still use the 6-speed transmission.)

    3. To my thinking, and supported by my research, there is contention between the ECM/AFM software and the TCM transmission shift control software. By disabling the AFM, in my case using the Range device, the harsh shifting problem may be resolved. My experience is that it will resolve the harsh shifting or “shuttering” in conjunction with the information in #4 below.

    4. Additionally, I noted that my transmission would run about 195F – 215F. According to numerous sources, predominantly Precision Transmission Service (PTS), excessive operating temperatures, towing in overdrive (which increases heat), and/or lack of maintenance are major contributors to the failure of the 8L90 transmission. PTS also states the torque converter is an issue on the 8L90, but I have no personal experience re the torque converter.

    To address these issues:

    (A) I drain and replace the transmission fluid and filter every 50,000 miles. Note that I have followed the recommendation to NEVER FLUSH the transmission which I have verified with other mechanics. Simply drain the fluid, replace the filter, and replace the same volume of fluid drained. (Yes, it’s a real PITA since GM no longer has fill tubes/dip sticks on the transmission.) (I acknowledge that the draining and replacement of the fluid only renews a portion of the total volume of the transmission, but I am not prepared to take the risk of flushing the transmission against the recommendations of others with more experience.)

    (B) I upgraded to the Superior STL010 SureCool Transmission cooling adapter on the flow block ($40 on eBay and literally 20 minutes to R/R) which reduced my transmission operating temperature on average ~45F year-round.

    (C) On my last transmission fluid change, I also added 10 oz. of LubeGuard 63010 as a number of reviews on the product mention the elimination of harsh shifting. (Again, my harsh shifting problem was resolved with the Range device, so the addition of the LubeGuard product was merely an additional precaution.)

    On occasion, when doing interstate travel I will remove the Range device just to see how the truck will perform. I have driven the same 750 mile round trip dozens of times, so I have a pretty good data base of information. While I do not have a heavy foot, on the interstate I will set the cruise control at 75 mph and let the truck run. On occasion, I will speed up to 85 mph to either pass or take advantage of long downhill runs.

    Most recently, I did the same 750 mile round trip within a couple weeks–ambient temperature of ~85F. With Range device installed the entire trip, I averaged 19.8 mpg. With the Range device removed (and AFM fully operational) I averaged 21.2 mpg. So the numbers align with my research that you can expect a 5-8% reduction in mpg with the AFM disabled. While the AFM does appear to work, I am willing to live with the lower mpg to avoid any potential issues with the lifters or the harsh shifting(see paragraph below).

    The interesting part is that with the AFM activated (Range device removed), the harsh shifting on either side of second gear returns–even my wife commented “What was that?” when we pulled off the interstate to refuel. Again, I attribute that to software contention between the ECM and TCM. Candidly, I think it is beyond resolution, even if GM had the motivation to resolve that issue, as GM has moved on to the 10-speed automatic.

    Therefore, I will stay with the Range device and the frequent oil and transmission fluid changes to minimize the opportunity for either (i) a lifter failure, or (ii) a $4000+ transmission failure. At 150,000 miles I will consider whether a new vehicle will be in order.

    1. I have a 2012 GMC Sierra with about 180,000 miles. I purchased an AFM bypass to fix the oil consumption problem. It worked but now I have an oil leak. There was no oil prior to the AFM bypass. Could bypass have caused this oil leak?

  36. I have a 2012 Chevy silverado 1500 5.3 4×4 with 266,000 miles and just recently developed a lifter tick.What is the best way and also best budget option to remove the AFM? This truck will be a daily driver but not towing anything big so I don’t need horsepower just need it back on the road.

Leave a Reply

Your email address will not be published. Required fields are marked *