Abstract: An air fuel ratio control system for an internal combustion engine having an electronic engine control module and an upstream and downstream exhaust gas oxygen sensor positioned in the engine exhaust gas stream. A first feedback loop includes the upstream EGO sensor. A second feedback loop includes a downstream EGO sensor and a trim bias signal to bias stored values provided from an air/fuel bias table. Such a biased signal is applied to an air fuel feedback controller which provides a feedback air fuel control signal to be applied to an open loop fuel controller.

Abstract: An exhaust gas oxygen sensor is used to control the air/fuel ratio of an internal combustion engine in combination with an electronic engine control. The exhaust gas oxygen sensor is positioned in the exhaust stream flow from the engine. The electronic engine control utilizes different air/fuel ratio feedback strategies depending upon whether the signal output from the exhaust gas oxygen sensor is saturated indicating a rich air/fuel ratio, saturated indicating a lean air/fuel ratio or operating in a linear region.

Abstract: An air fuel ratio control system for an internal combustion engine having an electronic engine control module and an upstream and a downstream exhaust gas oxygen sensor positioned in the engine exhaust gas stream. A first feedback loop includes the upstream EGO sensor and an air fuel bias table. A second feedback loop includes a downstream EGO sensor and a trim signal to change the stored values in the air fuel bias table.