OBD II Uart Hookup Guide
Resources and Going Further
Now that you’ve gotten the basics down for communicating with the OBD-II UART board, try modifying the example sketch to work with parameter IDs that are supported on your particular vehicle.
You can also work with some free software available online, that prints the data out into cool graphs and meters for you without any programming required, other than using a serial port. Check out a current list of freeware for OBD boards here.