Theory Of Operation

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

The Fuel Injection Pump (sometimes called the 'High Pressure Delivery Pump') is mounted on the Engine. It creates high-pressure fuel for the Fuel Rail, which supplies the Fuel Injectors. Fuel enters the Fuel Injection Pump from the electric Lift Pump, which is located inside the Fuel Tank. The Fuel Injection Pump has a built-in cascade overflow valve at the inlet that re-directs excess fuel accumulated during low-pressure delivery. Excess fuel is used to lubricate the Fuel Injection Pump and then returned to the Fuel Tank. The low-pressure fuel delivery continues on to the Fuel Quantity Solenoid (FQS).

The Powertrain Control Module (PCM) uses the FQS to meter the amount of low-pressure fuel entering the high-pressure pumping chambers inside the Fuel Injection Pump. The FQS works in tandem with the Fuel Pressure Regulator (FPR) to control fuel volume and pressure in the Fuel Rail. The FQS is mounted in the Fuel Injection Pump. The PCM supplies the solenoid with a 12 Volt supply and a Pulse Width Modulated (PWM) control circuit synchronized to the Camshaft position.

The FPR is positioned at the return passage of the Fuel Rail. The FPR default position is open when not being controlled by the PCM. When the FPR is open, it allows fuel pressure in the rail to escape into the return circuit and onward back to the Fuel Tank. When the PCM wants to increase Fuel Rail pressure, it commands the FPR to close, allowing fuel pressure to build up.

The PCM monitors fuel pressure at the Fuel Rail. The Fuel RAIL Pressure Sensor (FRPS) is a three wire 5-Volt sensor mounted on the Fuel Rail. The FRPS monitors the high-pressure fuel injection system. The PCM uses this value to calculate and adjust the amount fuel pressure in the Fuel Rail. The PCM is then able to maintain constant fuel pressure for proper Fuel Injector operation.

There are two separate approaches used for this monitor: The Standard Heat-Up (SHU) and the Rapid Heat-Up (RHU). Fuel economy and emissions are improved when the engine is allowed to reach a higher temperature. Engine performance and torque are increased when the engine is running at a cooler temperature. The PCM determines which heat-up mode to use based on various conditions.

The PCM uses the P0088-00 monitor when there is a Fuel Rail pressure-high occurrence during the SHU mode.

The PCM uses the P1290-00 monitor when there is a Fuel Rail pressure-high occurrence during the RHU mode.

Because the PCM switches between SHU and RHU mode, both DTCs may be present when flow-excessive is detected. Both DTCs have the same Diagnostic content.