I built an arduino setup using a few of these:
https://smile.amazon.com/SMAKN-MCP2515-Controller-Receiver-Protocol/dp/B012ET9E1U/ref=sr_1_2?ie=UTF8&qid=1525017291&sr=8-2&keywords=mcp2515
To hook in and passively monitor each of the 3 CAN buses on my 2018 Leaf. After successfully reading...