OK, I'm trying to determine exactly what's going on here. It's probably 1 of a couple of things.
* It could be that the file is signed, and it's checked by the firmware in the head unit. If this is the case, we're dead unless someone has a spare headunit they don't mind loaning to me.
* It could be that the application CRCs itself. If THAT'S the case, then we have a possibility. (I might find where this is done, and disable it).
So, to help me determine which of those is the case, I have prepared a test file. The steps for this are the same as they were for the hack above. Slap this on the card, and see what it says.
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(There's lots of slack space at the end of the file. I changed 1 byte of that. If the code checks itself, this should be fine. If the headunit is checking it, it'll still fail.)
(Just in case anyone is curious, the disassembly of this .dll is 9,544,014 lines long. There's lots of room for stuff to hide.