Abstract: A storing area of a non-volatile memory includes a plurality of blocks, in each of which a failure diagnosis frequency (numerator) and an operating frequency (denominator) are stored. The failure diagnosis frequency is the number of times failure diagnosis is executed, while the operating frequency is the number of times a vehicle enters a given operating state. When the vehicle enters the given operating state or the failure diagnosis is executed, rewriting is executed as incrementing, by one, the stored failure diagnosis frequency or operating frequency in a given block. When the operating frequency in the given block reaches an overflow threshold, the failure diagnosis frequency and operating frequency are reduced to half and written in a different block.

Abstract: A storing area of a non-volatile memory includes a plurality of blocks, in each of which a failure diagnosis frequency (numerator) and an operating frequency (denominator) are stored. The failure diagnosis frequency is the number of times failure diagnosis is executed, while the operating frequency is the number of times a vehicle enters a given operating state. When the vehicle enters the given operating state or the failure diagnosis is executed, rewriting is executed as incrementing, by one, the stored failure diagnosis frequency or operating frequency in a given block. When the operating frequency in the given block reaches an overflow threshold, the failure diagnosis frequency and operating frequency are reduced to half and written in a different block.