Ignition Switch

The signal to ECU indicating that the ignition switch is on, off, or cranking (ST) is signaled by ignition switch. When ignition switch on signal is input, the ECU energizes control relay coil and supplies power to sensors and actuators. When ignition switch ST signal is inputted to ECU, the ECU determines engine is cranking and controls fuel injection rate, idle speed servo control, ignition timing, etc. for optimum cranking conditions.