Gm Global Technolgoy Operations, Inc.

William J Morgan

John F Van Gilder

Martin Leven

Randall L Gallagher

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.

Method and apparatus for determining coolant temperature rationally in a motor vehicle

An improved assembly method and a corresponding diagnostic method carried out by an electronic engine control module in a factory test setting reliably and inexpensively verifies correct matching of a vehicle engine and an exhaust gas oxygen sensor installed on an exhaust pipe thereof. Heating elements within the oxygen sensors are manufactured so as to exhibit an electrical resistance that is different for each type of sensor. Due to normal part-to-part tolerance variation, the heater resistance of one type of oxygen sensor falls into a first range, and the heater resistance of the other type of oxygen sensor falls into a second range. The electronic control module for each engine is calibrated as part of its overall fuel control calibration, to recognize an oxygen sensor current requirement range corresponding to the respective fuel control (i.e., leaded or unleaded). The electronic control module operates during an initial period of engine operation during factory testing prior to convergence of the first and second resistance ranges to measure the average current supplied to the installed oxygen sensor, and to compare the measured current with the calibrated current requirement range. The comparison is used to set a diagnostic indicator, which is checked to determine if the engine should be directed to the next assembly area or returned to a repair area so that the correct sensor may be installed.

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DeWitt, MI, United States of America

William J Morgan