Abstract: A failure-detecting device detects failure of an air-fuel ratio sensor arranged downstream of a three-way catalyst in an exhaust passage of an internal combustion engine. The air-fuel ratio of an air-fuel mixture supplied to the engine is perturbed with a predetermined repetition period and by a predetermined amplitude. There is detected an amount of change in an output from the air-fuel ratio sensor responsive to the perturbed air-fuel ratio. Failure of the air-fuel ratio sensor is detected based on the amount of change in the output from the air-fuel ratio sensor.

Abstract: A system which monitors the performance of at least one HC sensor arranged in an exhaust passage of and internal combustion engine. According to a first aspect of the invention, a value of output from the at least one HC sensor is stored, which is assumed when the fuel supply to the engine is cut off, and a value of output from the at least one HC sensor is corrected by the stored value. According to a second aspect of the invention, the value of output from the at least one HC sensor assumed when the fuel supply to the engine is cut off is compared with a predetermined value, and if the former exceeds the latter, it is judged that there is abnormality in the at least one HC sensor.

Abstract: In an air-fuel ratio control method and apparatus for an internal combustion engine supplied with a gas mixture of air and fuel, in which an actual air-fuel ratio is determined from exhaust gas components by using an O.sub.2 -sensor installed in an exhaust pipe of the engine, and the air-fuel ratio of the mixture gas to be supplied to the engine is controlled through feedback control on the basis of deviation of the actually detected air-fuel ratio from a reference value (A/F=14.7). Performance of the O.sub.2 -sensor is determined by making use of change in the air-fuel ratio output of the O.sub.2 -sensor at a time of interruption of the fuel supply to the engine or at a time the fuel supply to the engine is restarted.

Abstract: A method of detecting deterioration of an exhaust gas ingredient concentration sensor for use in controlling an air-fuel ratio of a mixture supplied to an internal combustion engine having an exhaust system in which the sensor is arranged. The sensor has an output characteristic approximately proportional to concentration of a specific ingredient in exhaust gases emitted from the engine. The air-fuel ratio is feedback-controlled to a desired air-fuel ratio by calculating an amount of fuel supplied to the engine by the use of a desired air-fuel ratio coefficient indicative of the desired air-fuel ratio and set in dependence on operating conditions of the engine, and an air-fuel ratio correction coefficient set in dependence on a value of an output from the sensor and the desired air-fuel ratio coefficient. A plurality of average values of the air-fuel ratio correction coefficient are calculated, respectively, when the desired air-fuel ratio falls within a plurality of predetermined ranges.

Abstract: A device for determining activation of an air-fuel ratio sensor comprising an air-fuel ratio sensor arranged in an exhaust system of an engine and having a heater for heating an oxygen concentration cell element and an oxygen pump element, a current flowing means for flowing a predetermined current from a first electrode of the concentration cell to a reference electrode, a pump current controlling means for controlling current flowing in the pump element so that a sensor voltage between the reference electrode and the first electrode becomes a reference voltage, a pump current detecting means, a current flow cutting means, a sensor voltage detecting means, a heater power supplying means, and a timer means operated at every predetermined time interval for starting the heater supplying power means to the heater during a pump-current-cut state and for operating the current flow cutting means during the predetermined time interval.

Abstract: A device for determining activation of an air-fuel ratio sensor which comprises an air-fuel ratio sensor comprising an air-fuel ratio sensor comprising an oxygen concentration cell element and an oxygen pump element arranged in an exhaust system of an engine provided with electrodes and an interposing diffusion chamber wherein exhaust gas is diffused and introduced, and a heater for heating the oxygen concentration cell element and the oxygen pump element; a pump current controlling means for controlling pump current which flows in the pump element so that the electromotive force of the concentration cell element becomes a predetermined reference voltage; a pump current detecting means; a pump current cutting means; a pump voltage detecting means; a heater power supplying means; a memorizing means for memorizing a previous pump voltage allowable range for the pump current or a target air-fuel ratio of the engine; and a timer means operated at every predetermined time interval for starting the heater supplying

Abstract: The invention is directed to a system for electronically controlling (open loop and/or closed loop) an internal combustion engine of a motor vehicle. By means of at least one measuring unit at least one signal is generated representing the position of a power-determining component and the measuring unit comprises several sensors. The measuring unit is associated with a power-determining component of the vehicle such as a throttle flap or the control rod and/or accelerator pedal. The sensors are checked with respect to their functional capability by comparing the signal values generated by the sensors to each other with respect to a pregiven tolerance range. When a fault of one or more of the sensors is detected, then that sensor or those sensors which is or are unaffected can be determined.

Abstract: First and second air-fuel ratio sensors are disposed upstream and downstream of a catalytic converter respectively, and these sensors provide detection signals used to set first and second air-fuel ratio correction quantities, respectively, whereby an averaged air-fuel ratio corection quantity is calculated. During a steady operation in which a change in the averaged air-fuel correction quantity is below a predetermined value, a final air-fuel ratio correction quantity is calculated according to the first and second air-fuel ratio correction quantities. During a transient operation in which a change in the averaged first air-fuel ratio correction quantity exceeds the predetermined value, the second air-fuel ratio correction quantity is fixed from when the change exceeds the predetermined value until a predetermined time has elapsed after the change drops below the predetermined value.

Abstract: The invention is directed to a method for the temperature open-loop control and closed-loop control of exhaust gas probes for mixture control systems having several heatable exhaust gas probes. For this purpose, the temperature of one exhaust gas probe is closed-loop controlled in a control loop and the heaters of other exhaust gas probes are open-loop controlled. The closed-loop controlled exhaust gas probe controls the open-loop controlled exhaust gas probes insofar as the actuating variable of the temperature control loop is used as the output value for the temperature open-loop control of the other exhaust gas probes.

Abstract: In a method for determining at least one threshold voltage in controlling lambda one, this voltage is no longer set to a precisely predetermined value with the aid of a high-precision reference voltage source; instead, a counter voltage, connected in opposition to the probe voltage, is measured and the threshold voltage is referred or the threshold voltages are referred to the measured value and the absolute amount of the measured voltage does not have to be known. This method makes it possible to manage without a high-precision reference voltage source and without high-precision resistors. Instead, an arrangement according to the invention has a means for measuring the counter voltage and a means for referring threshold voltages to the counter voltage.

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust passage, the actual air-fuel ratio is adjusted in accordance with an air-fuel ratio correction amount calculated by using the output of the upstream-side air-fuel ratio sensor and an air-fuel ratio feedback control parameter such as delay time periods, skip amounts, or integration amounts calculated by using the output of the downstream-side air-fuel ratio sensor, and the calculation of the air-fuel ratio feedback control parameter is prohibited when the downstream-side air-fuel ratio sensor is in an abnormal state.