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.

Abstract: A method for monitoring engine coolant warm-up behavior utilizing a model-based algorithm which provides a moving threshold for accumulated air or accumulated fuel entering into the engine. The algorithm allows for coolant temperature monitoring under a wide range of transient and steady state driving conditions while maintaining safeguards that prevent a false detection. The accumulated air (or fuel) delivered to the engine during the warm-up interval is used to represent the total heat generated by the engine during the warm-up interval. A time-varying moving calculated accumulated air threshold is therefore defined which can deliver accurate pass-fail decisions in conjunction with a predetermined target temperature.