I don’t know how to get to debug / dev mode on a Tesla, but did come across this old post , on how someone was in a test drive, which did have this mode.
Now this is quite old, so a lot has changed, but am impressed that a lot of the components and foundational architecture was setup. I am particularly impressed how each cell in the battery pack and report its state. The BMS that you see is the Battery Management System - that firmware is separate from the car’s firmware.
You can see more photos and geek out online here.
And of course if you really want to geek out, then check out su-tesla , where Hemera has really has gone to party . I don’t know how to do this, and I have a lot of respect for Hemera to do this - she has a lot of guts. Also not sure what the wife would think about it and kick me out. Maybe. :)
And finally, from a more (relatively) recent update , the AutoPilot has a tremendous amount of data. As reported here, and you can see on the video below, the volume of data is massive, and quite interesting. For example, what decides there are 4 virtual lanes? The car below is a US car (the country code 840 is a ISO 3166 code ).