Electronic control unit having hold circuit and method therefor

A method of controlling an electric power supply in a vehicle having a microcomputer, a hold circuit and an electric power supply relay, the hold circuit holding a relay condition in response to a hold signal generated by the microcomputer, the method comprising step of:

• determining, based on a hold set signal generated from the hold circuit, whether the relay condition is held by the hold circuit;
• determining whether a vehicle speed and an engine speed are zero;
• and
• generating a cancel signal from the microcomputer to the hold circuit to thereby cancel the hold condition of the relay by the hold circuit, when the determining steps determine that the relay is in the hold set condition and the vehicle speed and the engine speed are zero.