| 摘要 |
An electronic control unit executes a program to perform a failure diagnosis as well as a vehicle control. On boot-up, diagnosis associated data is read from a backup memory and written in a RAM. The diagnosis associated data represents a failure diagnosis result previously backed up in the backup memory. When performing a failure diagnosis, the diagnosis associated data in the RAM is updated if needed, and an update flag is turned ON at updating. The presence of the update is checked using the update flag. Each time the update flag turns ON, the update flag is turned OFF and a timer is set to zero. The timer starts to measure an elapsed time. When the timer value exceeds a threshold value, it is determined that a predetermined time elapsed since the diagnosis associated data was previously updated. The diagnosis associated data in the RAM is then backed up.
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