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How to Delete or Disable Active Fuel Management (AFM) on GM Engines

 
LS Corvette engine - What is Active Fuel Management (AFM)?

(Image/Lethal Garage)

Active Fuel Management (AFM) is a trademarked General Motors technology that improves gas mileage by shutting down half of the cylinders under light-load conditions to reduce fuel consumption. It is also known as Displacement on Demand (DoD) or cylinder deactivation.

How Does AFM Affect Performance?

AFM is good for gas mileage and can be 5-7 percent more fuel-efficient under certain conditions.

So Why Turn it Off?

There are a few reasons:

  1. Many people find the four-cylinder sound annoying if their vehicle is equipped with a louder aftermarket exhaust.
  2. Some drivers want V8 power under their foot at all times.
  3. AFM lifters have a history of failing and oil consumption can be a problem.

How to Delete or Disable AFM on GM/Chevy Engines

There are two ways to disable or delete Active Fuel Management on your GM or Chevy Gen IV LS or LS-based Vortec engine—one is to install an AFM Disabler, and the second is to install an AFM Delete Kit. Here’s what you need to know:

1. Install an AFM Delete Kit

An AFM Delete Kit is recommended when an AFM lifter fails or when doing performance upgrades. It replaces the AFM components with standard parts.

When installing an AFM delete kit:

  • You MUST upgrade to a non-AFM camshaft because the cam lobes in the four AFM cylinders are ground differently. The engine will have 25 less pounds of compression in those four cylinders which can result in a misfire code.
  • You will need to turn off the AFM system using a computer programmer or custom tuning.
  • It’s a little more work, but it’s recommended that you plug the pressure relief valve in the oil pan.
  • It is also recommended that you switch to a standard-volume oil pump.

2. Install an AFM Disabler

An AFM Disabler is an electronic device that plugs into the OBD-II port, under the dashboard. It prevents the computer from switching over to four-cylinder mode. It’s a simple and effective way to turn off the AFM system and provides the added bonus of improving exhaust sound.

A disabler device should ONLY be used if the valvetrain is in good working order.

Engines with AFM use a high-volume oil pump. When you eliminate the AFM system, the extra oil is no longer needed. Excess oil will be pushed out of the pressure relief valve into the oil pan. This will spray oil on the bottom of the cylinder walls which can cause oil burning, especially in high-rpm engines.

Which Option is Best—a Disabler or Delete Kit?

As long as a lifter hasn’t started to fail, you can get by with a less-expensive disabler as preventative maintenance. If a lifter has already started to fail, an AFM delete kit and non-AFM components are the way to go.

GM/Chevy Engines Factory-Equipped with AFM

Engine DisplacementRPO Code
5.3LLY5LC9LH6LMGLS4
6.0LL76L77LFALZ1
6.2LL94L99

How to Identify AFM Engine Components

The AFM system can be identified by its components. Look for the following:

1. Valley Cover

The AFM cover is called the Lifter Oil Manifold Assembly (LOMA). It’s ribbed with solenoids on the underside. It also has an electrical connector on the back. (Non-AFM engines have a smooth cover.)

LS - Lifter Oil Manifold Assembly (LOMA)

2. Engine Block

All Gen IV engine blocks have AFM towers and oil passages cast in. However, they are only functional on engines that used AFM.

LS - AFM Towers

3. Lifters

AFM engines use special lifters for cylinders 1, 4, 6, and 7. They are taller and have special oil holes.

LS - AFM lifters labeled

Engines with AFM also use a special camshaft, a high-volume oil pump, and a pressure relief valve in the oil pan.

How Active Fuel Management (AFM) Works

How Active Fuel Management (AFM) Works

(Image/GM Media)

When engine load is low:

  1. The computer sends a signal to the LOMA.
  2. The LOMA solenoids open.
  3. Oil flows to the special lifters through the AFM towers.
  4. The oil collapses the plunger inside the lifter.
  5. The collapsed lifters will not engage the pushrods and both valves remain closed.

Since no air can get in or out, four cylinders provide no power. The engine is running on only four cylinders.

The AFM cylinders are opposite of one another in the firing order. In four-cylinder mode, they act like air springs and allow for smooth operation.

As engine load increases:

  1. The computer sends a signal to the LOMA.
  2. The LOMA solenoids close.
  3. Oil bleeds off the lifters.
  4. The lifters return to normal operation.

All eight cylinders are now powering the engine.

NOTE: Some parts are not legal for use in California or other states with similar laws/regulations.

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40 Comments

  1. Pingback: LS3 Engine Upgrade Guide: Expert Advice for LS3 Mods to Maximize Performance - OnAllCylinders

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  3. What if the pressure relief valve is stuck “OPEN” and the oil pressure never gets up to where it needs to be? I’ve got about 6 to 8 psi of oil pressure after the engine gets warm and I have to stop at a traffic light. NOT GOOD!!

  4. Is the Pressure relief valve replaceable? Does the Pressure relief vavle ever go bad??

  5. GM tried this on cadillacs about 20 years ago and if memory serves me correctly it was a disaster

  6. I got as high as 23mpg on the highway in my ’89 K1500 with 350ci and a five speed manual. How about if they just let us have a manual transmission agains for fuel mileage?

  7. I have a ’08 6.0L out of a Silverado with an aftermarket oil pan that has no provision for a pressure relief valve. What can I expect with the AFM in place, or, with AFM disabled (not deleted)?

  8. If the 4th cylinder lifter has failed, would driving it damage the engine? Would you get enough power to drive at freeway speeds? Our 2013 yukon with 47k miles just failed. Having it fixed now, just curious Seems like a problematic design. Very expensive repair too!

    • Just had my afm lifter fail had to drive 500 more miles home on 7 cylinders in my 6.0 lt chev.
      Just pulled it down in the garage there was no other damage , luckily.

  9. GM should recall every vehicle with this terrible design flaw! Every one of these engine will have a lifter fail, this is a travesty!

    • I didn’t have lifters fail, I had the 4 cylinders 1,4,6,7 have such blow by that my choice was a valve and piston job or a new motor. I went with the new motor for the warranty. I only had 81k on the motor. My 2002 I had over 298K on it with no engine related issues. I will be installing the AFM deactivator tonight when I get hoe.

    • I have a 2013 1500 with the LC9. has 92,000 miles and was just told I have cam and lifter failure. $8500.00 fix. Looking to tear down myself.

  10. AFM sucks I’m paying for a truck that has broke down twice replace the cam and lifters and now it’s broke down again 105000 miles never heard of that in a 350 Chevrolet.

  11. put tran fluid in oil for a day till lifter became active, had to change the fouled plug. changed oil , its all working now, but want to disable this sorry system.

  12. Chris Kenney says:

    I did a delete on an 07 avalanche and no have no power, any thoughts on what might be going on? I have had some say that it is the valves and others say that it is the cat’s plugged. I don’t know where to being to look for the problem.

    • Chris, when you did your delete, did you also change the cam at the same time? If you left the original cam in, the AFM cylinders will be down about 25 lbs. of cranking pressure because the duration is longer on those cylinders to being with to offset the AFM lifter design. You may eventually see a check engine light from a misfire code and the ECM dialing everything back to protect your engine.

      One alternative is to swap in one of the larger 6.0 non-AFM truck cams. If you are using VVT, you could use the NAL-12612273 (L92) cam. If you don’t have VVT, you could use part number NAL-12561721 (LQ9) along with a 4-pole 3-bolt 2005 Corvette cam sprocket p/n NAL-12586481 to make it compatible with your ECM.

      If you swapped in a LS9 cam, you will find it makes good power at the very top, but it’s actually down from 5,000 rpm and lower where the truck spends the majority of its time. If that’s the case, Summit Racing has dedicated truck cams that will increase power through the range…bottom to top…but the meat of it is in the mid-range where your engine spends the most time. Give the folks in Summit Racing’s tech department a call (330-630-0240) and they can work on a solution for you.

    • Mike Sinnett says:

      I just did the delete and replaced the cam as well. Still have no power. I have no clue what to do now. I have already dropped a lot of money on this truck (08 suburban). Any help would be appreciated.

      • Hello Mike, if you don’t have any obvious signs like check engine lights etc., there are couple different possibilities. If you installed a factory truck cam, there shouldn’t be any particular reason for it to be down on power. We recommend taking the truck to a local chassis dyno tuner and talking with them about a reflash.

        They may be able to find some of those missing ponies. If you installed a performance cam intended for a car, it may be bleeding off some low end compression. A tuner can often fix that as well by giving it some more ignition advance in these regions.

        We’ve written some articles on the various Vortec engine upgrade paths, such as this one on LQ4 and LQ9–it discusses some of the better options for choosing a cam intended for use in a truck. You can search our site by engine code to find some of the upgrade articles we’ve published and more are on the way.

      • You also need the disabler installed in your obd connector. You will be placed in derate if the ECM does not see the correct resistance from the ATF intake.

    • Michael Badame says:

      Chris,

      I had the same issue and had to have the AFM information deleted from the computer and the car tuned.

  13. Keith Belair says:

    Question – i just bought a 2005 Saab 9-7 with 5.3 v8, (same as GMC envoy) which came with AFM, the car runs fine, so if i just install the OBDII electronic device, is it just as likely that my lifters will still go bad? Im a little confused on the problems too, I’m reading that the 2007 pick-ups with 5.3 really had bad oil consumption and plug fouling problems, but is the 2005 5.3 that came in the trailblazers, envoys, and sabb 9-7s the exact same design as these pick-ups and prone to the same failures? I guess they also went to aluminum blocks in 2007, not sure if that has anything to do with this issues… thanks for the advice!

    • Keith Belair says:

      I guess what I’m really trying to ask is,, are there any cons/disadvantages to installing the AFM delete Electronic module? You mentioned that it will shoot oil into the pan and on the cylinder walls possibly causing some oil consumption… So i have a running vehicle and my only concern is making it as reliable as possible, should I disable the AFM or not?? thank You so much!

      • Hello Keith, if your lifters are still in good shape, an AFM Disabler is a good idea. When they are locked into position, they won’t wear further and cause issues down the road.
        The vehicles affected were 2007 to Feb. 2011 AFM equipped engines (Aluminum or Iron block-L94, LZ1, L99, LC9, LH6, L76, LFA, LMG, and LY5). The secondary pressure relief in the back of the pan began to open at 55 psi and was completely open by 75 psi.
        In October of 2010, GM added a deflector (p/n NAL-12639759) to keep oil from being sprayed directly on the rear cylinders.
        Another option is to plug it entirely if the AFM is already removed. It uses a M14 x 1.5 thread plug like Dorman 65217. More information can be found in the GM TSB bulletin number 10-06-01-008g. It also mentions a valve cover replacement with revised PCV valve design.

        • Keith Belair says:

          Wow, thanks for the wisdom,, i checked my VIN Code (position #8, M=LH6) and my 2005 Saab 9-7x does have the LH6 motor with iron block,

          Are you sure it’s only 2007 & newer motors? I’ve read at many websites that the GMCs envoys, Chevys and saabs did start to come with AFM in 2005 with the LH6 motor,It says here it started in 2006 on the saabs, then the pick-ups got AFM in 2007.
          http://www.autoserviceprofessional.com/article/91652/ticking-gm-v8-lifters-and-dtc

          There is no light on my dash or anything that indicates the system is active or exists, so it’s very confusing, I’m still not sure if my vehicle has it or not. I can’t really tell from driving. I guess I might have to call a dealership or GM to get a definite answer on this one.

          I won’t bother with blocking the relief valve. a little burning oil is a minor thing, my main concern is avoiding a multi-thousand dollar repair needed to the motor.

          • Keith, we’re happy to help. The LH6 in 2005-06 was a little different than the one used in 2007-09, but both had AFM. As a side note, the early ones had a 24x reluctor and plastic chain guide (good) vs. the later ones with 58x and the spring loaded tensioner (not so good).
            There is a note in the TSB that states the bulletin doesn’t apply to the LH6 used in the Rainier, Trailblazer, and Envoy due to a different design oil pan and AFM relief valve. Because your Saab is mechanically similar to the Trailblazer, we’d suggest that you are correct and no changes need to be made to the relief valve.
            At this state, a disabler would probably do what you need it to do. You can monitor the oil level on your dipstick for 3,000 miles to determine if the deflector or plug would be needed, but chances are you won’t based on the TSB.

          • Keith Belair says:

            yep, you are 100% Right, I called a local saab shop and they filled me in, in 2005 the trailblazer and clones have DOD (displacement on demand), My next issue is getting extra ignition keys on the cheap. Apparently all passkey III keys are not the same,, I bought one that said for 2006 impala assuming all pk3 would be the same, and I could not get it programmed in my saab 9-7,, so how I’m waiting on ones that specially said for saab 9-7. hoping they will work. will feel like a jerk asking the clerk at lowes to cut them again.

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  15. My 2013 GMC Yukon XL 6.2L is currently having a failed lifer replaced. It is being covered under warranty since I only have 72,000 miles on it. Since it is not costing me anything out of pocket, I did not go with the Delete Kit (did not want to spend the money). Once I get it back, could I install the Disabler safely. I would rather stay a V8 full time than deal with AFM issues in the future.

    • Keith, sometimes they will only replace one lifter rather than the whole set–If that’s the case, another lifter can fail again pretty quickly.
      You are correct. Install the disabler when you get your Yukon back and it will remain in good working order.

  16. Mike Fasano says:

    Brian, I just purchased and installed a remanufactured L76 AFM engine for my 2007 Suburban. We were getting a code that the cam position sensor was not functioning properly. Changing the sensor didn’t help. As it turned out one of the cam bearings was failing and causing the cam to wobble (my guess) which messed up the AFM and probably some other stuff too. The engine had 200K miles. As we were installing the sensors prior to installation in the vehicle, we noticed that there was no fitting on the oil pan for the oil level sensor. I asked my local Chevy dealer, from whom I purchased the engine, to find out why the oil pan lacked the fitting. They learned that the oil level sensor was necessary and that we were supposed to have been advised that we needed to reuse the original oil pan. Fortunately, the old engine hadn’t been shipped back to the remanufacturer. When we removed the oil pan from the new block, we noticed a metal shield covering the bottom of the block. In other words, the crankshaft and bearings were not visible. Is this the shield you referred to in a past post? Side note, after 200 hundred miles of trouble free driving the transmission failed so we had to replace that too. I am leaning heavily on installing the AFM disabler. Thanks.

  17. Scott Perdue says:

    We recently purchased an 08 Suburban and noticed some shuddering around crusing speeds, usually 45-55mph and highway speeds around 75mph. Took it to a shop and they advised that it could be due to the AFM system not functioning properly. We are looking into the AFM Disabler option, but my question is- how do we know if a lifter is already bad or not? The car runs great apart from the shuddering at those speeds. Would it be fine to go ahead with the AFM Disabler? Or is the shuddering indicative of failed/failing lifters that need to be replaced before moving forward?

  18. Eric Hansen says:

    Hi Brian,
    I bought a 2010 GMC Sierra 5.3L Truck in 2013 with 24K miles. Right now I have just over 77K miles with no lifter problems… Knock on wood… I am thinking of the AFM disabler. However I do have 7 year bumper to bumper warranty that covers this problem if I start to get lifter problems over the next 2 years.. On the other hand if get the AFM disabler installed I am pretty sure that I void the warranty from what I read on the policy. The problem I am facing is that I want to drive this vehicle for at lease another 77K and do not want to drive my vehicle with this AFM issue. What would you do if you were in my situation? Install the AFM disabler now or wait until my warranty just about to expire to get this AFM issue resolved?

  19. thanks brian love the info I’m thinking of buying a ford now

  20. Clinton Reed says:

    Hello. I have a 2011 Chevy Tahoe with the 5.3 Gen 4 LS (VIN Code 0) and I bought a CAM motion DOD/AFM delete kit, 3 bolt drop in CAM Motion stage 2 camshaft, VVT delete kit and finally a Diablo Predator 2 Premium for GM programmer. I was told that before I start the vehicle up I will need to have the AFM and VVT disabled in the ECU but that would require a custom tune from a tuner as the ECU cannot just be told that the AFM and the VVT is gone. I am trying to find out of this is true. Diablo says yes but they do not provide tunes. CAM motion says no just have to disable the AFM and VVT with a stock tune as the camshaft is not an aggressive camshaft but a drop in. There are no changes in the valves or the springs. I have also heard that the oil pump is to be changed and I have also heard that it does not matter. Very confusing stuff out there. Any advice that you could offer would be great. Thank you for your time.

  21. Robert Drum says:

    Have an ’06 Yukon with 5.3, original engine had bad knock, was told it was lifters so had them replaced. It was good for about 10 miles and started with same loud knock noise. Replaced the engine with remanufactured one and had the AFM turned off with a computer hooked to the ECU. Have misfire code and engine has what I would call a surge while driving. Is this due to the AFM being shut off? Didn’t really notice a loss in power other than the surging, (wondering if that’s the engine trying to switch between 4 and 8 cylinders).

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