Mixture Ratio Feedback System

Mixture Ratio Feedback System:

PURPOSE AND OPERATION
The mixture ratio feedback system is used for precise control of the mixture ratio to the stoichiometric point, so that the three way catalyst can reduce CO, HC and NOx emissions. This system uses an heated oxygen sensor in the exhaust manifold to check the air-fuel ratio. The Engine Control Module (ECM) adjusts the injection pulse width according to the sensor voltage so the mixture ratio will be within the range of the stoichiometric air-fuel ratio.

This stage refers to the closed loop control condition. The open loop control condition refers to that under which the ECM detects any of the following conditions and feedback control stops in order to maintain stabilized fuel combustion.

^ Deceleration

^ High-load, high-speed operation

^ Engine idling

^ Malfunction of heated oxygen sensor or its circuit

^ Insufficient activation of heated oxygen sensor at low engine coolant temperature

^ Engine starting

^ Heated oxygen sensor high output voltage