Mixture Ratio Feedback Control System

Mixture Ratio Feedback Control:

PURPOSE
The mixture ratio feedback system is used for precise control of the air-fuel ratio to the stoichiometric point.

OPERATION
The three way catalyst can then better reduce CO, HO and NOx emissions. This system uses a front heated oxygen sensor in the exhaust manifold to monitor the mixture ratio. The ECCS control module (ECM) adjusts the injection pulse width according to the sensor voltage signal. This maintains the mixture ratio within the range of stoichiometric (ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.

OPEN LOOP CONTROL
The open loop system condition refers to when the ECM detects any of the following conditions. Feedback control stops in order to maintain stabilized fuel combustion.
1) Deceleration and acceleration
2) High-load, high-speed operation
3) Engine idling
4) Malfunction of front heated oxygen sensor or its circuit
5) Insufficient activation of front heated oxygen sensor at low engine coolant temperature
6) Engine starting
7) High-engine coolant temperature
8) After shifting from "N" to "D"
9) During warm-up
10) When starting the engine