Methods and systems for detecting faults in temperature sensors on engine systems provided with equipment for treatment of combustion products of an exhaust effluent stream during engine operation include determining sensor faults from differences in temperature between sensors present in such systems over time. Estimated exhaust gas temperatures may be compared against real time temperature measurements to arrive at a diagnostic residual value representing the difference between a modeled value and measured value, and deviation of the measured value from the modeled value is used to indicate a sensor fault.