What switches power on to the starter solenoid when the ignition is engaged?

The ignition switch is the correct answer because it is the component responsible for initiating the starting process of the vehicle. When you turn the key in the ignition or press the start button, the ignition switch closes the circuit, allowing electrical power to flow to the starter solenoid. This action activates the solenoid, which in turn engages the starter motor to crank the engine.

The function of the ignition switch is critical, as it not only powers the starter solenoid but also other systems in the vehicle, such as the fuel system and electronic controls that are necessary for the engine to start and run properly. Understanding this component's role helps in diagnosing issues related to starting a vehicle.