An interface tool can be connected ECU in 3 different types. First is OBD (on-board diagnositcs), second is bench mode and third is bootloader mode. OBD is easiest way because you don't need to take ECU off to be connected. At the same time this mode shorten the period of operation. But bench and bootloader ways take longer time because the ecu must be removed, even the top case of ecu must be opened in bootloader mode. For learning more, please visit blog section and find all detail descriptions of connection types out