Once the ECM has determined how much fuel is required, it must next determine when to inject the fuel. Injection timing is determined by the ECM after considering input from the coolant temperature sensor, intake manifold air temperature sensor, and boost pressure sensor.
The ECM knows the cylinder position for timing because of the signal from the Engine Speed/Timing Sensors. The ECM adjusts timing for best engine performance, fuel economy and white smoke control. Actual and Desired Timing cannot be viewed with an Electronic Service Tool.
The ECM knows where top center on cylinder #1 is from the signal provided by the engine Speed/Timing Sensors. The ECM decides when injection should occur relative to top center and provides the signal to the injector at the desired time.