OBD-II UART question

Will the OBD-II UART product allow me to enter data into the vehicles OBDII bus or will it only allow me to read data from it?

It’s primarily for reading data from a vehicle, but depending on the vehicle, you may be able to write data back to the ECU.

How would I go about writing back to the ECU? Would it be done via software using the OBD-II UART or would I need additional hardware? Thank you