Component Functional Description - Powertrain Control Module (Pcm)
The PCM monitors the input signal from the Fuel Rail Pressure Sensor to determine the commanded duty cycle to the FPCM. On a fixed pressure system the commanded duty cycle is varied to maintain a constant pressure of 400 kPa (58 psi). On a variable pressure system the commanded duty cycle is varied to adjust fuel pressure based on engine needs. The PCM will command the operation between 11% and 89% duty cycle. Ambient temperature and fuel temperature can also contribute to fuel pressure changes. The pressure is raised during high ambient temperatures to prevent boiling of the fuel.
On vehicles with high pressure fuel systems, the PCM monitors the Fuel Pressure Sensor on the low pressure side of the system, not the Fuel Rail Pressure Sensor on the high pressure side.