I've been able to change (write zero) to the VSS*/4000 counter at $b657. I've also been able to erase the option byte at $b6c7 and write bit 2 there for the manual trans.
Edit: This entire paragraph is wrong, disregard. It seems like the 05 unlock is cleared after two 06 uploads are executed, or something... Presumably first being the write and second being the clear command to turn off the eeprom control register (turn off programming voltage). Whatever the case, it doesn't seem to be at all straightforward.
I'm playing around with writing obscene ascii messages to the unused FF bytes, and I'm learning a lot. Fingers crossed I can figure out what the "rules" are with this mode. If anyone has knowledge that applies to flash / mode 5/6 programming that I'm missing I'd love a bit of a nudge in the right direction.
All this considered, I'm somewhat afraid that erasing the odometer may be impossible without a patch to the (uveprom) firmware. Hope to have more, better news tomorrow.
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