First of all, thanks to all of the early backers for their support. Already halfway there!
This is just a small update, with a proof-of-concept video showing what works so far. Apologies for the poor audio quality — due to bad planning, I had to re-narrate over the whole thing with the laptop’s microphone : )
Summary / extra notes :
The bench ECU I use for testing is from a 2005 Sentra (ECUID: 6Z68A). In this video, I modify the stock ROM to a different ECUID, and alter some values in an unused portion of the ROM to make sure the checksum values are still valid.
The more straightforward method would have been to simply change the checksum values themselves. However, the method I chose could be used to avoid having to reflash the block containing the checksums when the intended modifications are in a completely different block; this reduces the number of reflash cycles (a limited resource).
As can be seen the process is pretty involved; the operations are fairly simple but tedious and error prone. Of course, improving this is what this project is all about!