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  1. #51
    Jr. Apprentice
    Join Date
    Aug 2011
    Location
    Lehigh Valley, PA
    Posts
    10

    Default Two things......

    1) Guess I'm one of "The 44,000". The AFM in my 2011/1500LT/5.3L/3.42/4WD works perfectly. There is no perceptible change in anything as it switches mode. It appears that, in general, when the instantaneous fuel usage rises above approximately 20mpg, it switches to V4, and then switches back to V8 when the instantaneous usage falls below approximately 18mpg. Unless you are looking at the fuel usage display in the DIC, there's no way anyone in the vehicle would know what mode it is in, or when it changes mode. When it's in cruise-control at a steady speed on mainly level roads in V4, a slight press on the accelerator immediately switches it to V8 until the accelerator is backed-off. Then it switches back into V4. I routinely get 17-18mpg in typical around-town driving. It has gone as high as 21.5 in mostly-highway driving. I do not drive like an idiot. Maybe that helps.

    2) For all of you having issues -- if your truck has a spec like mine (and perhaps others, I have no way to know), you very likely got new engine controller firmware pushed to your truck sometime in the last week or two. You might want to see if its behavior has changed lately. And yes, GM can push new firmware to your engine controller while it's sitting in your driveway. It does not require a visit to the dealer.

  2. #52

    Default

    I think it's great your getting that kind of mileage and can't tell when it switches modes. I did notice that you didn't list your mileage.
    I am curious about your occupation I am a master tech and have been for twenty years so anytime I am riding in any vehicle that changes sounds or hesitates just a little I make a mental note of it. So it's the little things that drive me insane sometimes.
    I still love the truck and wouldn't want to get rid of it. But again, I just want to know what's going on. The transition isn't seamless on mine I know it isn't. Am I going to take it back to the dealer? Not yet, but to think Chevrolet would push and update to the engine control module is just plain silly. Yes I know it's possible but due to the legality of what could go wrong by doing the upload and download it just won't happen.
    My credentials, I am a gm master tech And when we do any campaigns or safety recalls the vehicle has to be present and we have have your signature, and permission to change anything.
    Just my two cents.

  3. #53
    Jr. Apprentice
    Join Date
    Aug 2011
    Location
    Lehigh Valley, PA
    Posts
    10

    Default

    My profession is in electronics engineering in the Aerospace field. I KNOW -- not guessing -- that new firmware was pushed to my truck. While all those legalities you mention are nice window dressing, it IS possible (and easy, in fact) to push firmware updates invisibly and remotely through the OnStar system. (Which is yet another reason why I intend to disable that piece of crap.) Generically, since I don't know the procedure that GM uses, here's approximately how it's done: The new firmware is broken into small blocks, each with error-correcting bytes and/or a checksum, that are uploaded to the target one by one. On receipt, the checksum is verified and the verified block is held in RAM. When the final block is successfully received, the entire image checksum is verified and the ECU copies an image of the current firmware to RAM (just in case). The new image is then copied over and saved to the working NVRAM and processor execution is directed to the start point. That entire process of copying and restarting takes only a matter of tens to hundreds of milliseconds, and would occur only after a period of disuse. It's really quite easy and takes place in many many systems of all kinds every day. Bandwidth of the link is of no relevance because it affects only the rate at which code blocks are received. The internal error-correction routines (of which there are many types) take care of transmission errors. If the link is slow, it's entirely possible that the upload process could take hours or even a day or two. Ultimately, it doesn't matter because the process is self-correcting.

    Safety recalls are legally a whole different can'o'worms than a firmware update "for the convenience of GM". You ever hear of a secret warranty? Same thing here. They know something's not right, let's say, and want to fix it without fanfare and without causing a run of annoyed customers to the dealership for a warranty visit that costs GM $136.72. Simple solution? Push a firmware fix and hope that customers will suddenly discover that their AFM is now working well or maybe that ping in fourth going up the Maple Street hill has magically gone away. Most customers who were aware of the issue would probably chalk it up to "better gas" or something.

    It has 1500 miles on it. And little things drive me insane too. I'm a great believer in fixing things BEFORE they break and leave you stranded, waiting for the AAA truck. I'd read the various truck boards prior to going truck-shopping back in July and had a short list of things to look for (AFM, noise from the cabin air vent, etc.) and took an extended test drive of each truck I considered buying. I was pleased to find that none of the four had any of the problems of which I was aware. In fact, the truck I ended up with is completely problem-free. Even those little things that plague every manufacturer now and then like wheel balance or alignment are spot-on. I'm a pretty happy owner.

  4. #54
    Sr. Mechanic
    Join Date
    Oct 2011
    Location
    Salt Lake City, UT
    Posts
    158

    Default How do you know

    SR-
    I have had classes in computer networking and I am aware that everything you said is possible. However, how do you know for sure a firmware update was sent out and/or installed in you truck?

  5. #55

    Default

    blackcamaro, bigmike,

    Did you ever get any relief from GM regarding the widespread new GMC Sierra Silverado Escalade 5.3 liter six speed transmission ( clunking banging slamming ) active fuel management (AFM) that so many are complaining about?

    Most of these widespread issues appear to surface in the GM 2009 trucks and newer. Right around the time GM took the $54 Billion TARP bailout. Just before GM said they paid back the "loan" money (only $6 Billion of the $54 Billion bailout). That was very "genuine" of the Federally appointed CEO at the time!

    Odd how these complaints are widespread all over the net but nhtsa.gov doesn't list them much since 2009. nhtsa.gov, the same Federal organization that administers the new, in 2009, CAFE MPG standards.

    Maybe GM was trying squeeze MPGs out of their entire fleet, including trucks, at the expense of driveability? "Get that AFM out there in 2009, 2010, 2011 and 2012"?

    Pushing the 5.3 liter AFM computer controlled transmission on the market before they had the "quirks" (slipping, banging, slamming, growling, lagging, odd noise making) worked out of it to appease the FEDs?

    Been driving almost 30 years. This thing is unbelievablly annoying and very low quality.

    If you're looking at a new or newer GM truck, drive it in the mid 40 MPH range for an extended period of time. Determine how seamless the transmission and Active Fuel Management ( AFM ) is.

    Many new owners are very disappointed with that and many other quality control issues, driveabilty, excessive noise, rattles little Customer Support etc.

  6. #56
    Sr. Mechanic
    Join Date
    Oct 2011
    Location
    Salt Lake City, UT
    Posts
    158

    Default

    "Most of these widespread issues appear to surface in the GM 2009 trucks and newer. Right around the time GM took the $54 Billion TARP bailout. Just before GM said they paid back the "loan" money (only $6 Billion of the $54 Billion bailout). That was very "genuine" of the Federally appointed CEO at the time!"

    This exact sentence was over at another forum. They use the term "widespread" but if you do a google search you come up with very little. These are the same guys who don't want/wish to spend $300.00 on a custom tune to make the truck better. They get very irritated that GM sells 50,000 units a month GMC/Silverado combined.

  7. #57

    Default

    Quote Originally Posted by 94blackcamaroz28 View Post
    BigMike, I have the exact same problem with the gas pedal clicking. Did you ever take it to the dealership? I called the dealership yesterday, well actually called 2 of them to get warranty work and no one has returned my calls. Fancy that.

    I'm hoping they replace the gas pedal or do something. My wife and I just purchased a 2007 tahoe with AFM and the V8 to V4 transition is absolutely seemless. I agree with you that sometimes I have to goose the pedal in my silverado just to get the damn thing to transition back to v8 mode.

    ---------- Post added at 07:22 AM ---------- Previous post was at 07:20 AM ----------

    Disabling the AFM will void the warranty. Trust me if GM would disable the AFM I would gladly wait in line.

    The thing that worries me is taking it to the dealership. I'm sure without a SES light they will just ignore it. Dealerships have done it in the past....part of the reason I hate going. I can't imagine the gas pedal clicking normal. Our tahoe doesnt do it at all. It is seemless.
    When I called my dealer asking if they could disable the AFM the tech told me they could "probably" use a tuner and it wouldn't void my warranty and it would cost $400.....

  8. #58
    Sr. Mechanic
    Join Date
    Oct 2011
    Location
    Salt Lake City, UT
    Posts
    158

    Default

    Quote Originally Posted by gto3764 View Post
    When I called my dealer asking if they could disable the AFM the tech told me they could "probably" use a tuner and it wouldn't void my warranty and it would cost $400.....


    With all due respect....that is hardly a definitive answer. I don't think the Tech has the authority to speak for the dealership or GM.

  9. #59

    Default

    Quote Originally Posted by CKNSLS View Post
    With all due respect....that is hardly a definitive answer. I don't think the Tech has the authority to speak for the dealership or GM.
    Well, the tech is a representative of the dealer where I bought my truck and as they "Chevrolet" would be attaching the tuner and shutting the AFM or DOD whatever you wanna call it, I would have to say the warranty would remain intact. I would ask for that to be noted on my bill as well. I am more troubled by the $400 it would cost!

  10. #60
    Sr. Mechanic
    Join Date
    Oct 2011
    Location
    Salt Lake City, UT
    Posts
    158

    Default

    Quote Originally Posted by gto3764 View Post
    Well, the tech is a representative of the dealer where I bought my truck and as they "Chevrolet" would be attaching the tuner and shutting the AFM or DOD whatever you wanna call it, I would have to say the warranty would remain intact. I would ask for that to be noted on my bill as well. I am more troubled by the $400 it would cost!

    You can believe it. But in today's technology-that info will go in to the computer along with your VIN. All dealers have access to it as well as GM corporate.

    There has to be "buy in" on many different levels. Your dealer isn't going to be able to do the change without "buy in" from GM.

    I am in agreement that the $400.00 is steep.

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