For 1990-2009 cars

The function of the fuel metering system is to deliver the correct amount of fuel to the engine under all operating conditions. Fuel is delivered to each cylinder by the fuel injectors. The fuel injectors are controlled sequentially by the powertrain control module. The powertrain control module bases the control of the fuel injectors on several important engine parameters. These engine parameters include the following:

• | The mass air flow (MAF) sensor

• | The intake air temperature (IAT) sensor

• | The engine coolant temperature (ECT) sensor

• | The throttle position (TP) sensor

• | The engine speed (RPM)

• | The heated oxygen sensor (HO2S)

Determining the air density is critical to proper air/fuel management. The air density measurement is primarily derived from the MAF sensor input. For more information on the operation of the MAF sensor, refer to Information Sensors/Switches Description . The complete fuel metering system consists of the air/fuel delivery system as well as the electronic control system. For information on the electronic control system refer to Powertrain Control Module Description and Fuel Metering Modes of Operation .