VEHICLE ELECTRONIC CONTROL SYSTEM, AND METHOD FOR UPDATING PROGRAM USED THEREIN

Update data is acquired from an external instrument (10) to a master device (1), and the update data acquired to the master device (1) is written to a data storage side of a storage unit (201) included in an electronic control device (2) according to an instruction from the master device (1). After the update data is written to the data storage side, a first detection unit (102) is used to determine whether or not a vehicle is parked, and when a determination is made using the first detection unit (102) that the vehicle is parked, an instruction is given to the electronic control device (2) to activate a program stored in the data store side and rewritten with the update data. Then, when the program is activated according to the instruction to activate the program, a second detection unit (202) different from the first detection unit (102) is used to determine whether or not the vehicle is in a parking state, and when the second detection unit (202) is used to determine that the vehicle is in the parking state, the program is activated, thereby updating the program for the vehicle.