Theory Of Operation

WARNING: This page is about a different variant/trim than selected.

The Fuel Quantity Solenoid (FQS) works in tandem with the Fuel Pressure Regulator (FPR) to control fuel volume and pressure in the Fuel Rail. The FQS is positioned in the inlet side of the High Pressure Delivery Pump (HPDP). The solenoid receives both the 12 Volt supply and a duty-cycle ground signal from the PCM. The Powertrain Control Module (PCM) meters the amount of fuel entering the pumping chambers inside the HPDP. The FPR is positioned at the return passage of the Fuel Rail. The solenoid receives both the 12 Volt supply and a duty-cycle ground signal from the PCM. The FPR is normally open when not being controlled by the PCM. The Fuel Rail return passage opens allowing fuel pressure in the rail to escape into the return circuit and on to the Fuel Tank. When the PCM is controlling the FPR signal, the solenoid valve closes allowing fuel pressure to build in the rail.

The PCM monitors the idle fuel control system using two separate monitors. The first monitor will detect a failure if the idle control system cannot achieve or maintain the target idle speed (rpm's) within a calibrated tolerance. The second monitor will detect a failure if the idle control system cannot achieve the target idle speed with a fuel injection quantity within a calibrated tolerance. The injection quantity tolerance is a calibrated percentage of the normal injection quantity depending on engine speed, coolant temperature and selected transmission gear (i.e. park / neutral or drive / reverse).