SYSTEM AND METHOD TO REDUCE VEHICLE NOx EMISSIONS

An engine control system includes one or more oxygen (O2) sensors disposed proximate to a three-way catalytic converter (TWC) in an exhaust system of the vehicle, a nitrogen oxides (NOx) sensor configured to measure an NOx level of the exhaust gas downstream of the TWC, and a controller. The controller is programmed to determine a downstream O2 sensor control error, compare the O2 sensor control error to a predetermined threshold voltage, enable an NOx control logic if the O2 sensor control error is less than the predetermined threshold voltage, monitor the NOx sensor and integrate a measured NOx concentration for a predetermined time threshold or NOx flow threshold, determine a lambda compensation based on the integrated NOx concentration, and adjust an air/fuel ratio of the engine based on the lambda compensation to reduce NOx breakthrough.