Abstract: Methods, systems and devices for identifying irrational results from an engine coolant temperature (ECT) sensor in a vehicle are described. The vehicle suitably includes a processor in communication with the ECT sensor and an intake air temperature (IAT) sensor. The method includes the steps of receiving an ECT reading from the ECT sensor and a IAT reading at the processor, evaluating a temperature difference between the ECT reading and the IAT reading to determine if irrationality is present, and providing a fault indication in response to the evaluating step. The evaluating step includes monitoring the IAT reading during operation of the vehicle to identify the presence of an engine block heater if the temperature difference exceeds a pre-determined threshold.