Fuel Metering Modes of Operation

The basic function of the fuel metering system is to control fuel delivery to the engine. The fuel is delivered to the engine by individual fuel injectors mounted in the intake manifold near each cylinder.

The two most important inputs for fuel control are the Mass Air Flow (MAF) sensor and the Heated Oxygen Sensor 1 (HO2S 1). The MAF sensor provides the Powertrain Control Module (PCM) with engine air intake quantity, while the HO2S 1 provides the PCM with exhaust stream oxygen content information. The PCM modifies the air/fuel mixture by changing the injector pulse width signal sent to the injectors. By constantly measuring the air intake and the exhaust oxygen content and adjusting the injector pulse width, the air fuel ratio is kept very close to the optimal 14.7:1. This is the range at which the Three-Way Catalytic Converter (TWC) operates most effectively and at which the emissions of this vehicle are kept to a minimum. The constant tailoring of the air/fuel ratio is based upon feedback from the HO2S 1 and is referred to as closed loop operation.