EXHAUST GAS RECIRCULATION WIDE RANGE AIR FUEL SENSOR FOR RICH EQUIVALENCE RATIO TARGET RATIONALITY DIAGNOSTIC

A method for operating an exhaust gas recirculation system using rationality diagnostics for an automobile vehicle includes: estimating an oxygen storage content (OSC) of a catalytic converter of a vehicle; comparing an amount of oxygen stored in the catalytic converter to an OSC threshold; initiating a closed oxygen storage control (COSC) event for a predetermined one of multiple cylinders of an engine of a vehicle if the OSC threshold is met or exceeded, the COSC event targeting a rich air-fuel equivalence ratio (EQR) for the predetermined one of the multiple cylinders; and directing a fuel injector communicating with the predetermined one of the multiple cylinders to operate the predetermined one of the multiple cylinders at the rich EQR.