Patent ID: 7155326

Claim:
An electronic control unit comprising: a power supply circuit configured to receive an externally input first activate signal and a second activate signal and configured to output a first power supply voltage when it is determined that at least one of the first and second activate signals is in an active level, the power supply circuit being configured to interrupt the output of the first power supply voltage when it is determined that both the first and second activate signals are inactive levels, respectively; a timer circuit configured to: measure a period that has elapsed since the interruption of the output of the power supply voltage, turn the second activate signal from the inactive level to the active level when the measured period reaches a predetermined first setting period, the level of the second activate signal being changeable between the inactive level and the active level based on external control, and output a monitor signal associated with the second activate signal; and a computer operable based on the first power supply voltage output from the power supply circuit, the computer being configured to execute a fault diagnostic task by: controlling the timer circuit to change the level of the second activate signal between the inactive level and the active level during the active level of the first activate signal, and monitoring a level of the monitor signal output from the timer circuit to determine whether the level of the second activate signal is turned depending on the change of the second activate signal by the timer circuit based on the monitored level of the monitor signal.