Electronic circuitry and control algorithms are described to automatically establish the output voltage of a linear exhaust gas oxygen sensor (e.g., a UEGO sensor) corresponding to an exhaust air-fuel ratio of stoichiometry. The apparatus and control logic herein described may be used to adaptively correct the setpoint of an air-fuel ratio control system in which a UEGO sensor is used in a feedback loop to adjust the fuel injection quantity of an internal combustion engine.