Engine Timing

The powertrain control module (PCM) commands the fuel quantity. The fuel injector control module (FICM) controls the duration of the injection event and is shown as parameter identification (PID) FUELPW on the scan tool.

The PCM controls the injection pressure and fuel volume by varying the injection oil pressure with the injection pressure regulator (IPR). The command to the IPR is a 12-volt, pulse width modulated (PWM) signal controlled on the ground side.

The injection oil pressure command is shown as PID IPR which is the percentage ON of the PWM signal. The injection oil pressure is shown as PID ICP.

The PCM uses camshaft position (CMP) and crankshaft position (CKP) input signals to calculate the engine speed and position. The PCM conditions both input signals and supplies the FICM with the CMP and CKP output signals. The FICM uses the CMP and CKP output signals to determine the correct sequence for injector firing. The PCM sends information about the fuel demand, engine oil temperature (EOT), and injection control pressure (ICP) through the CAN to the FICM. The FICM uses this information to calculate the injection cycle.