SYSTEM AND METHOD TO REDUCE VEHICLE NOx EMISSIONS

A method of reducing nitrogen oxides (NOx) in an exhaust aftertreatment system having one or more oxygen (O2) sensors and an NOx sensor disposed proximate to a three-way catalytic converter (TWC), the one or more O2 sensors each being configured to measure an O2 level of exhaust gas produced by an engine, and the NOx sensor configured to measure an NOx level of the exhaust gas downstream of the TWC, the method comprising:

• determining, by a controller, a downstream O2 sensor control error;
• comparing, by the controller, the O2 sensor control error to a predetermined threshold voltage;
• enabling, by the controller, an NOx control logic if the O2 sensor control error is less than the predetermined threshold voltage;
• monitoring, by the controller, the NOx sensor and integrating a measured NOx concentration for a predetermined time threshold or NOx flow threshold;
• determining, by the controller, a lambda compensation based on the integrated NOx concentration;
• and
• adjusting, by the controller, an engine air/fuel ratio based on the lambda compensation to reduce NOx breakthrough.