I am developing an iOS app which enables me to store information of cars. I'm using an OBD-2 Bluetooth device to interact with my app.
There is a scenario where I need the value DTC or Diagnostic Trouble Code to be stored. Some blogs suggest that the value of DTC should only be fetched when the vehicle ignition is ON and shouldn't do it when the engine is running.
I need to know why that is an issue. What are the factors which needs to be noted while reading those DTC values?