Patent ID: 7475234

Claim:
A vehicle electronic control apparatus comprising: a microcomputer working to control a device mounted in a vehicle; a first power supply circuit operable to supply operating power to said microcomputer in response to input of an on/off signal switchable between an on- and off-state, upon input of the on/off signal in the on-state, said first power supply circuit starting to supply the operating power, upon input of the on/off signal in the off-state, said first power supply circuit stops supplying the operating power; a timer circuit including a register and a counter, the register storing therein a set value, the counter designed to star counting when the on/off signal is switched to the off-state, when a count value of said counter reaches the set value stored in said register, said timer circuit outputting a power supply on-signal to activate said first power supply circuit to supply the operating power to said microcomputer; and a second power supply circuit working to supply operating power to said timer circuit at all times, wherein when said first power supply circuit supplies the operating power to said microcomputer in response to the power supply on-signal outputted from said timer circuit, said microcomputer performing a given task and altering the set value as stored in the register of said timer circuit, and wherein said microcomputer alters the set value to outside a counting range of the counter to prohibit the power supply on-signal from being re-outputted; and when activated in responsive to subsequent input of the on/off signal of the on-state upon turning on of an ignition switch of a vehicle, said microcomputer makes a determination of whether the set value has been altered or not and diagnose the timer circuit based on a result of the determination.