Yesterday I got the new OLED screen and it works flawlessly with my Teensy.
Today the 2A fast blow fuses and their mounts came in today. Turns out the mounts don't quite fit a standard PCB hole pattern, so I soldered them inline with the wires from the OBDII cable, hot glued the mounts together, and then soldered a 4 position JST female connector on the end.
I then took it out to the car and tested the connections with my multimeter. First I verified that I was getting +12V from the power wires. Then I verified that there is ~60 Ohms resistance across the CANH and CANL lines (since there are two 120 Ohm terminating resistors in parallel on the CAN line - total resistance should be 60 Ohms). Looks like the wiring of the cable is good!
I also did some reading on Chassis GND vs Signal GND and decided there was no real need to use Signal GND. Because of this, I'm only using Chassis GND as my ground - Signal GND isn't being wired for this project.
Here are some pics:
