P59 flex fuel oddity

For some reason, when I flash a "calibration only" write to my car it usually remembers the last alcohol percentage from before the new flash. However, sometimes it goes to 0% and has to relearn its way back. The pcm in question is in a 2004 GTO that had a flex fuel patch added via other software before converting to an HPT 2bar sd OS. It has a content sensor in the feed line just before the rails and the appropriate wiring so that it works. I could understand if it went back to a default setting, such as the 38% setting for if the sensor errors out, or if it always zeroed. I just have no idea why it occasionally (but not most of the time) loses the content percentage memory when flashed. While on the subject, it would be nice if HPT gave access to the update rate tables for that sensor, as it takes a few minutes to fully update after filling up with a different E percentage. I have other ways of adjusting that, but it is a minor nuisance having to use multiple types of editing software because of all the tables HPT does not have.

I'm used to HPT never resetting it on a cal flash. Just like how HPT on purpose does not reset other learned values on a cal flash, such as LTFT, LTIT etc. When I used to run efilive it would reset all of those on a flash.

That would be so much more convenient if trims reset after a flash. Now that you mention it, I have no idea if trims reset along with the ethanol content on the odd occasion it does that. I usually already manually reset them before noticing the content % issue..

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Originally Posted by gametech

For some reason, when I flash a "calibration only" write to my car it usually remembers the last alcohol percentage from before the new flash. However, sometimes it goes to 0% and has to relearn its way back. The pcm in question is in a 2004 GTO that had a flex fuel patch added via other software before converting to an HPT 2bar sd OS. It has a content sensor in the feed line just before the rails and the appropriate wiring so that it works. I could understand if it went back to a default setting, such as the 38% setting for if the sensor errors out, or if it always zeroed. I just have no idea why it occasionally (but not most of the time) loses the content percentage memory when flashed. While on the subject, it would be nice if HPT gave access to the update rate tables for that sensor, as it takes a few minutes to fully update after filling up with a different E percentage. I have other ways of adjusting that, but it is a minor nuisance having to use multiple types of editing software because of all the tables HPT does not have.

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My p01 did the same thing. No big deal. I don't even pay attention to it anymore or at least I haven't noticed it doing it anymore

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Originally Posted by gametech

That would be so much more convenient if trims reset after a flash. Now that you mention it, I have no idea if trims reset along with the ethanol content on the odd occasion it does that. I usually already manually reset them before noticing the content % issue..

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agree 100%, all learned values reset would be better. the LTIT one is annoying, you have to set the min/max learned values to 0 or do a full flash or something to get it to reset (maybe disconnecting power from pcm works too).

just guessing, but probably 20+ years ago the collective preferred it the other way and it's just been the same ever since.

Quote:

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Originally Posted by gametech

For some reason, when I flash a "calibration only" write to my car it usually remembers the last alcohol percentage from before the new flash. However, sometimes it goes to 0% and has to relearn its way back. The pcm in question is in a 2004 GTO that had a flex fuel patch added via other software before converting to an HPT 2bar sd OS. It has a content sensor in the feed line just before the rails and the appropriate wiring so that it works. I could understand if it went back to a default setting, such as the 38% setting for if the sensor errors out, or if it always zeroed. I just have no idea why it occasionally (but not most of the time) loses the content percentage memory when flashed. While on the subject, it would be nice if HPT gave access to the update rate tables for that sensor, as it takes a few minutes to fully update after filling up with a different E percentage. I have other ways of adjusting that, but it is a minor nuisance having to use multiple types of editing software because of all the tables HPT does not have.

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If you have User Defined Parameters, you can use this XDF to change the update rate.

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Originally Posted by Pulse_GTO

If you have User Defined Parameters, you can use this XDF to change the update rate.

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Thanks, but since it is gen3, if I have to use a tunerpro xdf, I may as well just use freeware for the stuff HPT does not define. If I did much of anything with later model stuff, UDP might be worth paying for.