Paper Title: Virtual Exhaust Gas Temperature Measurement Abstract: Exhaust temperature models are widely used in the automotive industry to estimate catalyst and exhaust gas temperatures and to protect the catalyst and other vehicle hardware against over-temperature conditions. Modeled exhaust temperatures rely on air, fuel, and spark measurements to make their estimate. Inaccuracies or errors in any of these measurements have a large impact on the accuracy of the model. Furthermore, air-fuel imbalances, air leaks, ECT or ACT inaccuracies, or any unforeseen source of heat entering the exhaust may also have a large impact on the accuracy of the modeled estimate. Modern UEGO sensors have heaters with controllers in the UEGO ASIC to precisely regulate the oxygen sensing element temperature. These controllers are duty cycle based and supply more or less current to the heating element depending on the temperature of the surrounding exhaust gas. This paper proposes and analyzes a method for using the UEGO heater controller duty cycle to measure exhaust gas temperature at no incremental cost. The analysis shows that such a method can provide an accurate measurement of exhaust gas temperature both in nominal conditions and in the presence of an exotherm from unmodeled sources.