Failure determination apparatus and method and engine control unit for determining a failure of a temperature sensor

Abstract

There is provided a failure determination apparatus which is capable of determining the failure of a temperature sensor promptly and correctly regardless of environmental conditions at the start of an internal combustion engine. An ECU calculates an operation progress parameter indicative of a degree of progress of operation of the internal combustion engine from the start thereof. A RAM of the ECU stores a value of the temperature detected by the temperature sensor at a stoppage of the engine. Further, the ECU measures a stop time period from the stoppage to a start of the engine, and determines that the temperature sensor is faulty, when the difference between a value of the temperature detected by the temperature sensor at the start of the present operation of the engine and the value of the temperature stored in the RAM is equal to or smaller than a predetermined reference value on condition that the operation progress parameter calculated during the immediately preceding operation of the engine is larger than a predetermined value, and that the stop time period before the present operation of the engine is longer than a predetermined time period.