Based on information from various sensors, the ECM can
calculate the fuel amount to be injected. The fuel injector is a
solenoid-operated valve and the fuel injection amount is controlled by
length of injection time. The ECM controls each injector by grounding
the control circuit. When the ECM energizes the injector by grounding
the control circuit, the circuit voltage should be low (theoretically
0V) and the fuel is injected. When the ECM de-energizes the injector by
opening control circuit, the fuel injector is closed and circuit voltage
should momentarily reach the peak, and then settle at system voltage.