Which rule is used to send a signal to fire an electronic fuel injector?

The engine control module (ECM) is the correct choice as it is responsible for managing various engine functions, including controlling the fuel injection system. The ECM processes information from multiple sensors, evaluates the engine's current operating conditions, and then sends the appropriate signal to activate the electronic fuel injectors. This ensures that the correct amount of fuel is delivered to the engine cylinders at the right time, which is crucial for optimal engine performance and efficiency.

The fuel pressure regulator primarily monitors and maintains the proper fuel pressure but does not send signals to the injectors. The throttle position sensor provides data about the position of the throttle and informs the ECM about how much air is entering the engine, but it does not directly control the injectors. The mass air flow sensor measures the volume of air entering the engine, which helps the ECM make decisions about fuel delivery, but it is not responsible for sending the signal to fire the injectors itself.