This repository has the arduino code for use with nano can PCB.
These were created as a cheap device for people to get into car hacking.

I take no responsibility for any issues caused if using either the hardware or the code

Requires the use of the following Arduino library

https://github.com/coryjfowler/MCP_CAN_lib

The can-receive-all sketch is the receive example from the above library which will show all messages on the CAN bus. CAN speed can be changed from 500kbps.
CAN messages are shown on the Serial Monitor
This can be used to find interesting messages

The nano-can sketch is configured for the OBD2 port speed (500kbps) and will listen to the can bus starting with CAN ID 0x128. Both can be changed in the code.
Whilst on the Serial Monitor it will show the changes between the messages

u and d will change the CAN ID up or down by 1
U and D will change the CAN ID up or down by 16
h shows the above information

The nano-slcan sketch is slcan compatible software but the serial chip on the arduino boards I use will only run at 57600bps

Schematic Note:
Arduino Nano goes on the top with the URL on.
MCP2515 Module goes on the bottom but DO NOT solder the Terminator Jumper or CAN pin headers to the PCB
You may require a jumper on the Terminator resistor
L goes to OBD2 pin 14
H goes to OBD2 pin 6
Completed Top
Completed Bottom
OBD2 connector
PCB Top

PCB Bottom