The fuel metering system consists of the following components:

When the ignition switch is in the ON position (before engaging the starter), the PCM energizes the fuel pump relay for two seconds, causing the fuel pump to pressurize the fuel system. If the PCM does not receive ignition reference pulses (engine cranking or running) within two seconds, it shuts OFF the fuel pump relay, causing the fuel pump to stop.

The fuel rail assembly attaches to the engine intake manifold. The fuel rail assembly performs the following functions:

The top-feed fuel injector assembly is a solenoid operated device, controlled by the PCM, that meters pressurized fuel to a single engine cylinder. The PCM energizes the injector solenoid, which opens a ball valve, allowing fuel to flow past the ball valve, and through a recessed flow director plate. The director plate has multiple machined holes that control the fuel flow, generating a conical spray pattern of finely atomized fuel at the injector tip. Fuel is directed at the intake valve, causing it to become further atomized and vaporized before entering the combustion chamber. An injector stuck partly open can cause a loss of pressure after engine shutdown. Consequently, long cranking times would be noticed on some engines.

The fuel pressure regulator is a diaphragm operated relief valve with fuel pump pressure on one side and regulator spring pressure on the other side. The fuel pressure regulator is vented to atmosphere. A software bias is used to compensate injector on-time because the regulator is not referenced to manifold vacuum. The injector pulse width varies with the signal from the MAP sensor. With the ignition ON and the engine OFF, system fuel pressure at the pressure test connection should read 380-420 kPa (55-61 psi). If the pressure is too low, poor performance could result. If the pressure is too high, excessive odor and a Diagnostic Trouble Code (DTC) P0132, P0152, P0172 or P0175 may result. The Fuel System Diagnosis table has information on diagnosing fuel pressure conditions.

The throttle body assembly attaches to the intake manifold. The throttle body controls air flow into the engine, thereby controlling engine output. The air control valve mounted on the throttle body opens the throttle valve within the throttle body. Engine coolant flows through the coolant cavity on the bottom of the throttle body in order to prevent throttle valve icing during cool weather operation. The throttle body also provides the location for mounting the Throttle Position (TP) sensor.

The TP sensor is mounted on the side of the throttle body opposite the air control valve. The TP sensor senses the throttle valve angle and relays that information to the PCM. Knowledge of throttle angle is needed by the PCM to generate the required injector control signals (pulses).