Diagnostic method for a shaft sensor in a reciprocating internal combustion engine

Abstract

An improved method of diagnosing shaft sensor failure in a reciprocating internal combustion engine verifies engine rotation by sensor information responsive to dynamic variation in engine air intake that occurs during engine rotation. Failure of the shaft sensor is diagnosed when the dynamic variation in engine air intake is detected in the absence of a shaft sensor signal. The sensor information used to detect the dynamic variation in intake air may be obtained from either a mass air flow sensor disposed in a throttle passage of the engine, or from a pressure sensor disposed in an intake manifold of the engine, and virtually all current engine control systems utilize at least one of these sensors. The dynamic variation is detected by recognizing rising and falling segments of the signal waveform, by comparing the relative manifold pressure to predetermined maximum and minimum values, or by using a derivative of the signal waveform to recognize its inflection points.

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