A diagnostic system and method that (a) that uses models indicative of both successful firing and skips to determine if cylinders of a skip fire controlled internal combustion engine have successfully fired or successfully skipped and (b) uses filtered exhaust gas pressure readings for detecting faults associated with EGR systems and/or turbocharger systems.

An emissions test system includes an emissions analyzer, a contamination index module, and a diagnostic module. The emissions analyzer is configured to determine a concentration of an emission in a sample of exhaust gas from an engine. The contamination index module is configured to determine a contamination index based on at least two of a flow rate of the exhaust gas sample, the concentration of the emission in the exhaust gas sample, an operating duration of the emissions test system, a pressure of the exhaust gas, and a temperature of the exhaust gas. The diagnostic module is configured to identify potential contamination of at least one of the emissions test system and a component in the emissions test system based on the contamination index.

A fluid quality sensor for measuring a quality of a fluid comprises a measurement section mounted to an output side of a pump for the fluid.

A method for checking the plausibility of a pressure sensor that, during the measurement of a differential pressure, records measured values, whereby the measured values from the pressure sensor are compared to reference values for the differential pressure calculated on the basis of a model; whereby in order to determine the plausibility, at least one deviation of the measured values from the reference values and a difference between a first slope of the changing measured values and a second slope of the changing reference values over the curve of the measured values are taken into account.

A method of determining an abnormality of a differential pressure sensor which is configured to detect a pressure differential between an upstream side and a downstream side of an EGR valve provided to an EGR passage of an engine, is provided. The method includes the steps of controlling an opening of the EGR valve based on an output value of the differential pressure sensor, determining the abnormality of the differential pressure sensor based on the output value of the differential pressure sensor, controlling at least a throttle valve of the engine toward a closed side so that the pressure differential is maintained at a given pressure or higher when determining, and prohibiting the execution of the abnormality determination when an engine speed is a given engine speed or higher, and permitting the execution of the abnormality determination when the engine speed is less than the given engine speed.

A diagnostic system and method that (a) that uses models indicative of both successful firing and skips to determine if cylinders of a skip fire controlled internal combustion engine have successfully fired or successfully skipped and (b) uses filtered exhaust gas pressure readings for detecting faults associated with EGR systems and/or turbocharger systems.

Methods and systems are provided for detection of cylinder-to-cylinder air fuel ratio imbalance in engine cylinders. In one example, a method may include indicating air fuel ratio imbalance in an engine cylinder based on a comparison of an estimated cylinder acceleration for the cylinder and a calibrated cylinder acceleration for each of the engine cylinders. The indication of imbalance may be further confirmed based on one or more of an exhaust air-fuel ratio, an exhaust manifold pressure, and an individual cylinder torque weighted by respective confidence factors.

A gas sensor has a structure in which a sensor body is secured to a sensor-mounting member using an attachment screw. The gas sensor is capable of ensuring the stability of installation of a protective cover. The gas sensor includes the sensor body in which a sensor device is disposed and the cylindrical attachment screw disposed on an outer circumference of the sensor body to be rotatable. The gas sensor is secured to the sensor-mounting member which has an internal thread engaging the attachment screw and a bearing surface disposed on a front end side of the internal thread. The sensor body has a flange which protrudes outwardly on the front end side of the attachment screw. The flange held between the bearing surface of the sensor-mounting member and the attachment screw in the axial direction. A protective cover is secured to the attachment screw closer to the base end side than an external thread engaging the internal thread is. The protective cover covers an outer periphery of at least a portion of the sensor body which is closer to the base end side than the sensor-mounting member is.

A system and method are provided for testing and verification of an exhaust system. The system and method introduce a low pressure flow of gas into the exhaust system through an adaptor that fits into or about an exhaust pipe of the exhaust system. The low pressure gas can then be used, in the absence of engine noise, heat, and/or dangerous exhaust gases, to determine if one or more leaks exist in the exhaust system.

A gas sensor is equipped with a solid electrolyte body, a pump electrode, a sensor electrode, and a heater. In the gas sensor, a region of the whole of a front end portion of a heater base in which a heating element is disposed is broken down into three regions: an intermediate region defined between a front end and a base end of the sensor electrode, a front end region located closer to a front end side than the intermediate region is, and a base end region located closer to a base end side than the intermediate region is. A resistance value per unit area of a heating element lying in the base end region and a resistance value per unit area of the heating element lying in the front end region is selected to be higher than that of the heating element lying in the intermediate region, thereby keeping the temperature of a region around the sensor electrode at a desired level even when the temperature of gas changes.