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 peak, and then
settle at system voltage.
