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Thread: Why is my car entering DFCO mode when it shouldn't be??

  1. #1
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    Why is my car entering DFCO mode when it shouldn't be??

    I've found that my 2012 Impala (3.6L LFX engine, 6-speed trans) acts a little strange (fluctuating RPMS, etc) when exiting DFCO mode in certain cases, so I'm trying to reduce the number of situations in which DFCO mode is enabled (by raising the enable and disable RPM criteria). However, I'm finding that the car is still entering DFCO mode, even when my RPMs are significantly lower than my "Enable RPM" value - and I have no idea why...

    Here is my DFCO table:
    2012Impala-DFCOSettings.jpg

    And I've attached a log file. In the log file, DFCO is enabled from frames 6575-6678 and 22622-22775.

    Are the DFCO parameters just not working or are there cases were DFCO can get enabled regardless of the DFCO settings?

    Thank you in advance!!

    EDIT: Also attaching my Scanner config file and tune file, just in case (no longer using mailorder tune).
    Last edited by jtrosky; 06-15-2015 at 06:26 AM.

  2. #2
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    Can anyone help with this? I'm still finding that DFCO is being enabled even when my RPMs are well below my "Enable RPMs". Makes no sense to be. Seems to come on above 1200 RPM regardless of my RPM enable setting. Am I missing something? Are there situations where DFCO would come on even if the RPMs are lower than the Enable RPM setting?

    Thank you!

  3. #3
    Tuner cp-the-nerd's Avatar
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    I've had the same issue with DFCO being unresponsive to changes I've made. Hopefully someone can offer a good explanation for you. (Long winded *bump*.)
    2017 Chevy SS 6.2L/6M

  4. #4
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    I've found that changing the Enable RPM just doesn't seem to work (or at least not fully). The enable temperature and MPH parameters do seem to work however.... There are very few cases in which I want DFCO to activate - manly just during high speed "coast" situations (where the DFCO entry/exit isn't noticeable), so I've raised my Enable MPH to 57 in gears 5 and 6 only (I think) - at least that way, it only seems to enable if I'm going over 57mph (regardless of the RPMs, which, like I said, do not seem to actually work). I still need to work on the disable MPH settings though.

    Would still love to know why the Enable RPM setting isn't working though!

  5. #5
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    Actually, I take that back! I was just reviewing a log from yesterday and even though I have the DFCO enable MPH speed set to 57 in 6th gear (and RPM enable set to 1700), DFCO still enabled in 6th gear @ 49mph and 1136 RPM! So I'm guessing that the only DFCO parameter that actually works is the Enable ECT.... Strange - and frustrating!

    Is this something that I should talk to HPTuner support about? Or is it possible that some of these parameters just aren't supported by the ECM?

  6. #6
    Tuner in Training
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    Please explain to me why you even want to disable DFCO mode? it is a small but valuable fuel saving feature. How is it currently hurting you?

    Before you say fluctuating RPMs... are you 100% sure it is caused by this?
    Last edited by JerryPH; 07-27-2015 at 01:50 PM.

  7. #7
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    Yes, I'm 100% sure it's caused by DFCO. I've noticed that sometimes when exiting a highway, for example, after drifting for a while on the exit ramp, my RPMs would jump up and then a few seconds later they would go back down to where the originally started. I always assumed that it was the trans shifting strangely (feels like a shift when it enters/exists). Then, it happened one day while logging and sure enough, the RPMs jumped up when I entered DFCO and then shortly thereafter when back to where they started when I exited DFCO mode (there is a status bit that shows the DFCO status, so I'm 100% sure that it what it was) - and there was no shifting occurring when the RPMs jumped up and then back down.

    It's not that it "hurts" me - I just don't like the way it feels - at all - like I said, I always thought it was the transmission acting strangely until I saw what was going on in the HPTuner logs. Not one bit concerned with the fuel I'm saving during that 5 second span... I just want to tune it so that it doesn't enable and then disable so quickly like that. If it's going to active for 20 or 30 seconds while coating, that's one thing, but I feel it's just too "sensitive" the way it is. I've never experienced something like it with any other car I've owned either...

  8. #8
    Tuner in Training
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    It seems that there is a lot going on with this car that you don't like... lol

  9. #9
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    Of course I'm going to try and tailor the tune to my liking - thats the beauty of being able to tune things. If I don't like something, I fix it! :-)

    Why wouldn't I want to tune out things that I don't like?

    Do you have any idea of why the car is entering DFCO even when the parameters to do so aren't met? That was my question, not whether or not you think it's something that I should worry about or not...

  10. #10
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    I never could get DFCO working like I wanted - even though I'd set the enable RPMs to 1700 (for example), it would still enable at 1200 RPM sometimes. Never could figure out why, so I just disabled it completely (via the enable temp table). Now I *never* enter DFCO, which is fine with me (now, smooth coast-downs now!).

    Howerver, can disable DFCO cause any issues? I've noticed that sometimes while coasting down a large hill for example, my STFT's will max out (35, I think) when in closed loop - is this an issue? Why do the STFTs max out like that? I think it happened even when DFCO was enabled, but it seems to happen evern more now that DFCO is disabled... LTFT's are fine (between -5% and +5%).

    Thanks!