App uses OBD2 Bluetooth plug, it has ELM327 V2.1 IC that connects to all OBDII protocols. The app reads common PIDs, DTC (faults) and VID. To add PID you can use https://en.wikipedia.org/wiki/OBD-II_PIDs#Bitwise_encoded_PIDs Code based on bluetooth example.
The USB diagnostic plug:
https://www.ebay.co.uk/itm/14406005...xJr6rvr/9fEwx5GR4lwXqjvTE0|tkp:Bk9SR-6KtsKEYQ
The USB diagnostic plug:
https://www.ebay.co.uk/itm/14406005...xJr6rvr/9fEwx5GR4lwXqjvTE0|tkp:Bk9SR-6KtsKEYQ