In a method of operating a drive device, a probe temperature of an exhaust gas exhaust gas probe in an exhaust tract is measured, as the exhaust gas probe is heated by a probe heater. A temperature growth value representative of an increase in temperature of the exhaust gas probe is determined during heating of the exhaust gas probe, and the presence of a defect of the probe heater is recognized, when the temperature growth value deviates from an input value.

A method for diagnosing a lack of engine oil includes determining, by a controller, whether an oil level of an engine is normalized from an insufficient state to a normal state using an oil level switch. When it is determined that the oil level is normalized to the normal state, a driving mode of a vehicle is confirmed. When it is confirmed that the driving mode of the vehicle is an engine off driving mode, a diagnosis of the oil level is stopped.

A computer for a motor vehicle able to be electrically connected to a sensor of the vehicle over a wired communication link in order to receive an output signal generated by the sensor. The sensor being electrically powered by a power supply module via a wired power supply link. The computer is able to be electrically connected to a measurement device configured for measuring the variations in the electric current flowing through the wired power supply link, and it is configured for detecting a short-circuit on the wired communication link between the wired power supply link and the wired communication link, for receiving, from the measurement device, the measurements of the variations in the current flowing between the power supply module and the sensor and for estimating the output signal from the received current variation measurements.

A method for plausibilizing a rail pressure sensor value of a rail pressure sensor of an internal combustion engine having a common rail system that has a fuel high-pressure piston delivery pump includes acquisition of the beginning of conveying by the piston delivery pump, calculation of the rail pressure from the compression work performed by the piston, and plausibilization of the rail pressure outputted by the rail pressure sensor on the basis of the calculated rail pressure.

A heat-ray type of airflow meter has a signal processor for converting a detected intake air quantity into a frequency signal. An engine controller has a conversion table for converting the frequency signal into an air quantity. The signal processor and the conversion table have features such that the frequency increases as the magnitude of a positive air quantity increases, and the frequency decreases as an absolute value of a negative air quantity increases. In the conversion table, a prescribed positive air quantity value is assigned a dummy output for frequencies lower than a prescribed threshold value. Under normal circumstances, frequencies lower than a minimum value are not used. The frequency decreases to near 0 Hz when there is a disconnection or a short circuit, the dummy output is therefore output, and an injection quantity equal to or greater than a misfire limit is ensured.

Various methods are thus provided for identifying degradation in a fuel system. In one embodiment, a method of operating a fuel system comprises applying a pulse to a fuel pump responsive to detecting that lift pump pressure corresponds to a fuel vapor pressure, ceasing application of the pulse responsive to detecting that the lift pump pressure corresponds to a relief setpoint pressure, and indicating degradation in the fuel system if the detected lift pump pressure deviates from an expected fuel rail pressure, including distinguishing among degradation in the fuel pump, a lower pressure fuel pressure sensor, a fuel rail pressure sensor, and a pressure relief valve.

Methods and systems are provided for monitoring fuel level indicator noise in a sealed fuel tank system. In one example, the method includes comparing the outputs of a fuel level indicator and fuel tank pressure sensor in a sealed tank. If the outputs of both the fuel level indicator and the fuel tank pressure sensor outputs are noisy, then it may be determined that the fuel level indicator noise is mechanical in nature. However, if the fuel level indicator output is noisy while the fuel tank pressure sensor output is not noisy in the sealed tank, then it may be determined that the fuel tank pressure sensor noise is electrical in nature.

A method and test device for recognizing detecting whether a mass air flow meter of intake air of an internal combustion engine is defective is provided. In the method and device, a test procedure is executed using a pilot controller while a mixture controller that is used in non-test engine operation is deactivated. The pilot controller for the mixture of fuel and air in the respective cylinders outputs control values which, during normal operation of the internal combustion engine via the mixture control, are varied on the basis of a mixture deviation of the current mixture from a stoichiometric mixture. The engine is set to one or more different idling speeds and at each respective idling speed the mixture deviation is detected. If the detected mixture deviation(s) (i'lA.) satisfy a predetermined criteria thresholds, the air flow meter is identified as defective.

A method and apparatus for field testing and diagnosing at least one NO.sub.x-sensor in a diesel engine exhaust system are disclosed. The field testing apparatus is connectable to a truck having a lean burn diesel type engine, via an on-board diagnostic connector. The field testing apparatus is arranged to initiate a test cycle, and to diagnose at least one NO.sub.x-sensor in an exhaust system of the truck. The test cycle is performed on a running engine as a test sequence in a stationary truck, in at least two different states of operation, while NO.sub.x related values issued by the at least one NO.sub.x-sensor are measured over a predefined period of time. At least one state of operation is obtained by simultaneously opening the exhaust gas recirculation valve and controlling the back pressure valve for increasing backpressure. A dedicated algorithm is used to compare the measured values to a predefined model, and to provide a numerical summary and statistical evaluation of the sensor functioning. The numerical summary being indicative of a likelihood of the at least one NO.sub.x-sensor behaving correctly, and thereby enables a well founded decision as to whether or not the at least one NO.sub.x-sensor requires replacement.

To quickly determine whether or not the propulsive force of a vehicle drive source is abnormal. The onboard control device pertaining to the present invention has a drive manipulated variable detection unit for detecting or estimating a drive manipulated variable manipulated by a driver in order to impart a propulsive force to a vehicle, a command value calculation unit for calculating a command value for a drive source of the vehicle on the basis of the drive manipulated variable, a propulsive force control unit for controlling the propulsive force of the drive source on the basis of the command value, operating state detection units for detecting or estimating the operating states of the drive source, a drive manipulation rate of change calculation unit for calculating the rate of change in drive manipulation, an operating state rate of change calculation unit for calculating the rate of change in the operating state, and an abnormality detection unit for detecting abnormalities in at least the drive source on the basis of the rate of change in drive manipulation and the rate of change in the operating state.