I recently bought a 2015 Silverado 1500 with the 5.3L V8. It has the Active Fuel Management (AFM) system so it goes into V4 and back into V8 while driving which seems to be a good idea in theory but maybe not so much in practicality.

I've been reading on the GM Truck forum about reprogramming the computer to deactivate the AFM and tuning the rest of the engine to run more effectively in constant V8. I'm not worried about warranty issues because my truck is past the mileage point as it has 37K on it.

Has anybody here done this? If so, what tuning method/system did you use, local performance shop or mail order OBD plug?

I know the engineers designed it to run the way it does but there are also many reports of potential issues; failing lifters, excessive engine vibration, problems with the high pressure fuel pump. I'd like to try and avoid these if possible.

Thanks as always for this awesome forum!

I had that system in our 2008 Yukon XL which we recently traded in and it sucked big time. 1 quart of oil every 1,000 miles. When the engine went to 4 cylinders, it put more pressure on the other 4 cylinders and the oil blew by them. We sold it at 120,000 miles.
On the other hand, I have the same setup in my 2010 Silverado, GM made some changes after the 2008 model and I have not experienced the problems I had with the Yukon. I have 76,000 miles on my truck to date.
Like you, once I came across the articles on this subject, I read everything I could find out about it. If you do get yours retuned please post what they did and if you think it is a good idea.

Just to let you know, your truck is NOT out of warranty. It should have a 5-year/100,000 mile powertrain warranty.

I am going to keep apprised of this thread as I have always liked the theory of AFM and start stop technology but like you I question the practicality.

I don't own a vehicle with either of the technologies but am curious what comes up in this thread or what you find.
Also to see some real world outcomes as the in laws have a 2017 Suburban.

I'm interested in this thread as well having just traded into a 2016 Silverado. I'm a bit overwhelmed by all the new technology. I should probably spend some time at the GM Truck forum.

quote:

Originally posted by PowerSurge:
Just to let you know, your truck is NOT out of warranty. It should have a 5-year/100,000 mile powertrain warranty.

You are correct sir. Some of performance tuning shops offer to restore the stock programming if necessary. I'm not sure if the service department at the dealer would be able to detect any modifications though.

I give this info just to let others know what other manufactures have experienced with their cylinder management systems. Also what the manufacture is doing about it, if anything.

Honda has had many complaints of shuddering when their cylinder management system kicks in on their 3.5 V6 engines. It was a common complaint when I bought my Pilot a few years ago and at the time their was no "fix" or concern from Honda on this. Honda claimed normal operation at the time. I have owned other Honda vehicles with the 3.5 V6 without the cylinder management system and never had any issues with them. So I took my chances with the Pilot since most complaints seemed to be a personal preference thing and not all vehicles seemed to experience it. Personally I never experienced the shudder issues.

I have a Honda with the cylinder management system. 2011 Pilot. I just found info that they have been known to push oil pass the piston rings and cause misfires in cylinders 1-4. This was not going on a few years ago. Honda has recently put an 8yr unlimited mileage extended warranty on the Pilot engines because of this after having multiple complaints. Their procedure is to flash the computer. If the misfire code returns at a later date, but still has to be within extended warranty period/guidelines, then they will perform the ring repair. In other words if the misfire code returns outside the 8yr mark then your screwed.

I had a misfire code in cylinder 3 a couple of weeks ago. When I was poking around internet for cause of the code (usually its a bad coil or fouled plug) I came across the extended warranty info. Called the two local Honda dealers and one said they would just go ahead and perform the warranty ring repair whether or not it had been flashed (we bought the Pilot used about 3yrs ago from a GM dealer). The other advised they would have to flash the computer and if the misfire returned, within the 8yr period, then they would perform warranty ring repair. So of course I took it to the dealer that said they would do the warranty work no matter being flashed already or not. It had not been flashed when the Tech checked it on the drive for the service writer.

The timing belt was due to be changed per mileage. I had already contacted both dealers on pricing about a week before the engine light came on with misfire code. I always do my own repairs when possible but due to time restraints and not being able to have a vehicle down I was going to have the dealer replace timing belt, they offer a free loaner with the repairs. It worked out well for me. Because Honda has to remove all the timing belt items to access the heads for the pistons. So I only had to pay for any parts/labor not included with warranty repairs.

The following is what I paid for..
- timing belt kit (timing belt, serpentine belt, water pump, tensioner, pulley, crankshaft and camshaft seals)
- 2 spark plugs and labor for the two (warranty covered the other 4 with labor)
- front valve cover gasket (the rear cover removed to access the rear cylinders for the rings on 1-3 under warranty)
- valve lash adjustment, recommend when replacing the timing belt due to mileage
- labor for water pump
- labor for camshaft and crankshaft seals

The following is what Honda paid for (and most were due to be changed/replaced due to mileage, so this saved me a good bit of funds)...
- coolant
- oil
- oil filter
- 4 plugs and labor (these are platinum plugs. Honda charges $400 to replace all 6 plugs. Of course if you DIY then your looking at plug cost only at about $30-$40 each.)
- upper and lower intake manifold gaskets (these will start to leak at some point past the 100K mark. I have experience with these engines and have replaced them in the past on other vehicles)
- one valve cover gasket, as explained above they will start to leak after 100K.

For a little less then what they would charge for just the timing belt replacement I was able to do all the above and save some funds due to the extended warranty.



Hope this helps.

Side note...........My parents had an '84 Cadillac with the GM 4/6/8 V8 engine. It would turn off a pair of cylinder down to 4 for gas savings. They bought it used around '87-88 with low miles. They drove that car for years and put 200K plus on it. I actually took a few dates out in it. Very comfortable car. Don't remember it having great gas mileage. But it ran great and they never had any issues with the engine. Point is the technology has been around for several decades now. Like any vehicle and any tech sometimes there are issues sometimes not.

The GM AFM system has most bugs worked out by this time. Lifter collapse can still be an issue but it is still rare. I have only witnessed a handful of failures at this time amd only in the first 2 year ranges. 07 cadillacs and 08 everything else.

The oil consumption problem was not blow by caused by the AFM directly. There is an oil pressure relief valve in the oil pan that would spray oil directly under the pistons on the driver side of the motor. GM forgot to put a cap on it so it would spray down back into the pan. The driver side valve cover was redesigned as well, the old style cover had the pcv valve pick up in a spot right next to an oil passage and it would just suck oil into the intake manifold. The new design moves the pickup and adds several baffles to prevent oil from being sucked into the intake.

I have personally fixed dozens of GM vehicles with oil consumption issue and had several years of the same customer returning to make sure it wasnt losing oil between oil changes afterward. 2015 does have some changes from the earlier engines and they may have quirks of their own I've not witnessed yet but the AFM and oil consumption problems are fixed.

Tuning out the AFM wont do anything about the collapsed lifter issue. Unless you have the lifters changed out as well, if they start to leak and can no longer hold oil pressure they will still collapse. Its not as common as the internet would have you believe though.

I have a 2009 Z71 with AFM. Haven't had any issue with it that I know. It has 130k on it. I don't believe it using oil but I am also not militant about checking it. I get it changed every 5k or so.

I did have to replace the oil pressure sensor (part 12673134) and cleaned the filter (wasn't bad.) Not sure if its failure that had anything to do with AFM or not.

My biggest problem is that AFM just doesn't really work very well.

You could lug the engine when in 4 cylinder operation. It can also happen in an 8 cylinder if the load becomes too great and the RPM's drop.

This will result in the pistons cocking in the cylinder and causing them to wear an elongated pattern and decreasing the life of the engine.

I use a vacuum gauge on my truck to monitor the vacuum which will show the engine response and it also helps to improve gas mileage and tells you when to down shift to prevent lugging the engine resulting in longer engine life.

Talk to blackbear tuning. I have had two tuned by him and have been extremely happy with them. He focuses on GM stuff.

quote:

posted February 27, 2018 10:31 AM Hide Post
The GM AFM system has most bugs worked out by this time.

Hope so. They've been working on cylinder deactivation since the L62 8-6-4 was introduced in 1981.

quote:

Originally posted by Jaywendland1981:
The GM AFM system has most bugs worked out by this time. Lifter collapse can still be an issue but it is still rare. I have only witnessed a handful of failures at this time amd only in the first 2 year ranges. 07 cadillacs and 08 everything else.

The oil consumption problem was not blow by caused by the AFM directly. There is an oil pressure relief valve in the oil pan that would spray oil directly under the pistons on the driver side of the motor. GM forgot to put a cap on it so it would spray down back into the pan. The driver side valve cover was redesigned as well, the old style cover had the pcv valve pick up in a spot right next to an oil passage and it would just suck oil into the intake manifold. The new design moves the pickup and adds several baffles to prevent oil from being sucked into the intake.

I have personally fixed dozens of GM vehicles with oil consumption issue and had several years of the same customer returning to make sure it wasnt losing oil between oil changes afterward. 2015 does have some changes from the earlier engines and they may have quirks of their own I've not witnessed yet but the AFM and oil consumption problems are fixed.

Tuning out the AFM wont do anything about the collapsed lifter issue. Unless you have the lifters changed out as well, if they start to leak and can no longer hold oil pressure they will still collapse. Its not as common as the internet would have you believe though.

Thanks for all of the info!

Have a 2010 Pilot, with 133K on it.

The first 20K or so miles it would shudder occasionally when it did the 6-4 cyl change...especially on one hill, that I encountered right off my I-15 on ramp.

Never noticed ANY excessive oil consumption though.

The shudder is now nonexistent...motor now broken in?


Have the AFM on my 2017 Camaro SS. I get 20+ mph on average, with no shuddering or any other issues. So at least on the 6.2 liter V8 they must have it figured out.

quote:

Originally posted by hbabler:
Talk to blackbear tuning. I have had two tuned by him and have been extremely happy with them. He focuses on GM stuff.

They are the ones I am leaning towards. Have you taken your vehicle(s) in to the dealership afterwards and if so, have they given you any trouble with warranty work?

quote:

Originally posted by hbabler:
Talk to blackbear tuning. I have had two tuned by him and have been extremely happy with them. He focuses on GM stuff.

I looked around regarding tuning for my 2011 Z71 a while ago and this was the overwhelming response on GM forums from what I could see.
The local mechanic at our Chevy dealership here has a Supertuner for his older generation Chevy (2006) and it does seem much easier. Doing your own tuning on the fly and not mailing stuff back and forth. He said it made his drive like a whole new truck.

I can't seem to notice any benefit to AFM, it only turns on when coasting down hill and I still only get 14-15mpg so it can't be doing much.

I went ahead and ordered the device from Black Bear Performance. As a point of reference, this morning coming into work, I was able to hit 21 MPG for the "Last 50 Miles average MPG". I'll report back after the tuning is applied.

Glad I popped in this thread.
I may have to sen in the PCM for my 2000 Silverado for the traditional tune.
Sounds like it smooths everything out nicely with a little mileage bump.

So I got the tuned files and re-programed my truck last night. Took it for a quick spin just to make sure it would still drive. Good to go and I got to work this morning. I am in no way a gear head so hopefully the following is informative or at least entertaining. And this is by no means an endorsement for any product.

Prior to getting the tuned files, I had to send them the factory ECM (Engine Control Module) and TCM (Transmission Control Module) files along with a data file that contained info captured while I was driving. You use the AutoCAL device to collect these files and then I had to transfer them to my laptop. All cables are included. You have to use the "EFI Live" application to transfer the files from the device to your laptop and then back again when you get the new files.

I e-mailed them the files last Tuesday, 3/6, and they e-mailed me the tuned files yesterday, 3/13. They sent 2 different ECM files, one for low octane fuel and one for 91 and above octane fuel. I loaded the 91 octane ECM. They sent one TCM file.

The AFM is turned off and shift points have been changed. It seems to me that it holds a little longer in the lower gears, 2nd and 3rd but then goes through 4th, 5th and 6th pretty quick. It seems to have more pep getting up to highway speed and it does not "lug" as much and downshifts more effectively. I'm a pretty conservative driver anyway so I think this will work. Fuel efficiency on the way to work was at around 18-19MPG.

2008 Honda Odyssey with the cylinder management. Other than the Eco light on the dash, I’ve never noticed performance degradation. Just ticked over 141k miles. Last month, ring job. I’m beyond the extended warranty for the engine, but they did the job at 90% discount.