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.

Abstract: An improved method of determining and preserving soak-related time intervals of an internal combustion engine resets a continuous timer at the end of each engine run period, and reads the value of the continuous timer at specified events during an ignition key cycle. The method measures and preserves the engine soak time preceding the current and previous ignition key cycle, and determines an extended soak time that includes intervals of engine operation that are too short to significantly affect the engine thermal and fuel vapor purge conditions. The determined soak-related times are then utilized by various engine control and/or diagnostic algorithms, such as a hot re-start fuel control algorithm.

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.

Abstract: An improved test method for an EGR system reliably detects debilitating EGR system restrictions without significantly degrading combustion stability and exhaust emissions. The EGR valve test opening for diagnostic purposes is initialized at a relatively low value, which is progressively increased if the resulting change in intake manifold pressure fails to exceed a threshold based on the minimum expected change in intake manifold pressure for an EGR system that is regarded as functioning within acceptable limits. As soon as the measured pressure change exceeds the threshold, the EGR system is deemed to pass the restriction test, and the test method is terminated. If the EGR valve opening reaches a maximum value without the measured pressure exceeding the threshold, the EGR system is deemed to fail the restriction test, and a fault indication is generated.

Abstract: An improved method of determining and preserving soak-related time intervals of an internal combustion engine resets a continuous timer at the end of each engine run period, and reads the value of the continuous timer at specified events during an ignition key cycle. The method measures and preserves the engine soak time preceding the current and previous ignition key cycle, and determines an extended soak time that includes intervals of engine operation that are too short to significantly affect the engine thermal and fuel vapor purge conditions. The determined soak-related times are then utilized by various engine control and/or diagnostic algorithms, such as a hot re-start fuel control algorithm.