Known unused sections of calibration files...

Bosch Motronic etc ECUs and PCMs
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Known unused sections of calibration files...

Postby ironduke » Tue Apr 27, 2021 12:43 pm

Kind of an oddball question, lol.. Someone was starting a discussion on another post and I believe the gist was they wanted to be able to choose the CVN of each segment and have it pass checks.. The Checksum isn't so important as that's not given with scan tool requests, it's the CVN that is checked.. I did a quick search but I didn't see it being discussed.. Kind of got me curious so I poked around a little.

With 2 bytes somewhere in the segment it appears I am able to make the CVN pretty much whatever I want it to be.. Problem is I don't know for sure the 2 bytes I chose are unused.. Yeah, at the end of each segment there's usually a lot of ff's that can probably be used, except for the last segment of the bin because that has 8 bytes that are used.

Any way to know for sure? This started with an E67 ecu but I could see this being attempted on E38's E92's, etc... The header of each segment has a bunch of info in it, but does anyone know for sure if there's 2 bytes not used for anything there? or am I pretty much guaranteed that if I go to the end of the segment and count back 8 bytes and use those 2?

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Re: Known unused sections of calibration files...

Postby Tazzi » Tue Apr 27, 2021 4:13 pm

Maybe give a bit more leeway just incase, and count back like 12? Maybe? But best to compare with multiple vehicles with that OS to ensure that section of a cal is safe to use.
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Re: Known unused sections of calibration files...

Postby ironduke » Wed Apr 28, 2021 10:13 am

Tazzi wrote:Maybe give a bit more leeway just incase, and count back like 12? Maybe? But best to compare with multiple vehicles with that OS to ensure that section of a cal is safe to use.



Thanks, I actually pulled 20 out of my head and used that, seemed to work ok for 2 test files..

I'm thinking of checking before any writing is done there to sheck for a string of ff's there, should be a somewhat decent way to make sure it's unused and I'm not stepping on something.. make sense?

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Re: Known unused sections of calibration files...

Postby Tazzi » Wed Apr 28, 2021 12:26 pm

Yeah it does make sense. Generally speaking though, if doing custom edits, best option is to hard code which operating systems are support for such custom edit, as you will know that it will use the exact same layout for that OS.

This is effectively what they do for custom OS upgrades (2-3bar ect)
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