Things are going great, im nearly done on the arduino script.
Using CAN Hacker i was able to locate 3 key CAN message ID's of interest to me,
- one with general gearbox state that is transmitted all the time 0x489
- one that is used by the diagnostics tool to transmit, 0x6A9
- and one that is used by likely the BSI to reply to requests by the diag tool, 0x689
I was then able to 'decode' how the readings where being sent back by looking at changes while triggering a change in the reading via a switch or gear shift.
And put this all into an arduino sketch to emulate the process of requesting diagnostics readings, 'translating' them into readable data, and displaying/logging them for review.