Abstract: An automotive system has a primary control module, such as an engine control module (ECM) configured for connection to a malfunction indicator lamp (MIL), and a secondary control module, such as a transmission control module (TCM), each in communication with each other over a bus. Each control module includes a respective diagnostic data status record. Each record includes a pending fault field, a confirmed fault field and an MIL control status field. An improved method for synchronizing the diagnostic data contained in the respective status records includes an extended status signal set that is used to communicate over the bus. The set includes a diagnostic testing complete signal, a fault present signal and a MIL request signal indicative of a request to illuminate the MIL. Logic in the receiving control module (ECM) interprets the extended status signal set to properly synchronize its diagnostic data status record with the TCM's, including both pending and confirmed faults.

Abstract: A default value of transmission input speed in a motor vehicle powertrain having an automatic-shift multi-gear ratio power transmission is continuously updated based on a measured value of the input speed and other reliable speed data including transmission output speed and engine speed. The default value is substituted for the measured input speed when a malfunction of the input speed sensor is detected, and transitions back to the measured input speed when the input speed sensor malfunction is no longer present.

Abstract: A default value of transmission output speed in a motor vehicle powertrain having an automatic-shift multi-gear ratio power transmission is continuously updated based on a measured value of the output speed and other reliable speed data including transmission input speed and vehicle speed. The default value is substituted for the measured output speed when a malfunction of the output speed sensor is detected, and transitions back to the measured output speed when the output speed sensor malfunction is no longer present.

Abstract: An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. When the engine idle speed error magnitude is less than a calibrated threshold, usage of high DI fuel is detected by identifying a surge signal based on the engine speed error fluctuation in a predetermined frequency range attributable to combustion instability due to the presence of high DI fuel in a cold engine. When the average amplitude of the surge signal exceeds a calibrated surge threshold, the presence of high DI fuel is detected. Additionally, the method is disabled for a prescribed period following commanded load transitions associated with the air conditioning system and the automatic transmission.

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 engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. The usage of high DI fuel is detected during an engine idle period following starting by monitoring the engine speed to identify an engine speed excursion more than a calibrated percentage below the desired idle speed. The detection method is enabled under specified environmental conditions, provided the engine run time is greater than a specified time and the engine temperature is within a specified range. Additionally, the method is disabled for a prescribed period following commanded load transitions associated with the air conditioning system and the automatic transmission.

Abstract: An improved engine fuel control detects combustion instability due to the use of high driveability index (DI) fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. The usage of high DI fuel is detected during engine cranking by measuring the time required for the engine speed to increase from a lower reference speed to an upper reference speed, provided the engine run time is less than a calibrated value. A timer is started when the lower reference speed is achieved, and the timer value is compared to a crank time threshold determined as a function of the initial engine coolant temperature. If the timer value exceeds the crank time threshold before the engine speed reaches the upper reference speed, the presence of high DI fuel is indicated, and the air/fuel ratio is temporarily enriched.

Abstract: An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. When the engine idle speed error magnitude is less than a calibrated threshold, usage of high DI fuel is detected by identifying a surge signal based on the engine speed error fluctuation in a predetermined frequency range attributable to combustion instability due to the presence of high DI fuel in a cold engine. The speed error fluctuation content in the predetermined frequency range is identified with a Butterworth bandpass filter, and the bandpass filter output is low pass filtered to identify an average amplitude of the surge signal. When the engine speed error magnitude exceeds the calibrated threshold, the inputs of bandpass and low pass filters are set to zero.

Abstract: An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. The usage of high DI fuel is detected during engine cranking by measuring the time required for the engine speed to increase from a lower reference speed to an upper reference speed, provided the engine run time is less than a calibrated value. A timer is started when the lower reference speed is achieved, and the timer value is compared to a crank time threshold determined as a function of the initial engine coolant temperature.

Abstract: An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. The usage of high DI fuel is detected during an engine idle period following starting by monitoring the engine speed to identify an engine speed excursion more than a calibrated percentage below the desired idle speed. The detection method is enabled under specified environmental conditions, provided the engine run time is greater than a specified time and the engine temperature is within a specified range. Additionally, the method is disabled for a prescribed period following commanded load transitions associated with the air conditioning system and the automatic transmission.

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: A method of validating a leak detection test for a fuel tank in a vehicle includes the steps of determining a vacuum decay rate of a fuel vapor in the fuel tank and dividing the vacuum decay rate into a set of adjacent segments distributed over a series of consecutive time intervals. The method also includes the steps of determining a slope of the segments, determining if a difference between two consecutive slopes of the segments meets a predetermined criteria, and validating the leak detection test if the difference meets the predetermined criteria.