Abstract: The invention relates to a connecting circuit for a potential-free oxygen probe having a low-potential line and a high-potential line and includes: an amplifier; an offset voltage source connected to the high-potential line forward of the amplifier for applying an offset potential to the high-potential line; the amplifier having an input connected across the high-potential and low-potential lines to receive the difference between the potentials on the lines as an input voltage; the amplifier being adapted to amplify the input voltage and having an output for supplying an output voltage equal to the difference between the offset voltage and the amplified input voltage; and, the offset voltage being selected so as to cause the output voltage to always be greater than zero but less than a pregiven threshold voltage. This connecting circuit makes it possible to determine faults for probe connections, for example, short circuits of the line to ground.

Abstract: A digital control unit, in particular an ignition and/or injection control unit for motor vehicles, is provided. The control unit has a microcomputer (10) and a permanently connected main storage (12) containing control data and operating programs. This main storage unit (12) is designed as a read/write memory (RAM, EEPROM or the like). A control program that runs when the control unit is switched on is provided in an auxiliary storage (13) designed as a permanent storage (ROM, EPROM or the like). Based on a load instruction, the control program controls the loading of the main storage (12) from an external storage medium via an interface (21). The control program also automatically transfers the operating program access of the microcomputer (10) to the main storage (12). In this manner, software modifications can easily be subsequently implemented in the control unit when, for example, improvements or variations in program data or characteristic data are available and desired.

Abstract: A heated exhaust gas oxygen sensor assembly for an internal combustion engine that changes the heater status in order to detect a malfunction of the heater. The assembly includes an oxygen sensor, heater, impedance sensor, and controller. The oxygen sensor has a sensing element and a pair of output leads. The sensing element detects the relative oxygen concentration in the exhaust gas and responsively provides an oxygen level signal on the output leads. The heater physically warms the oxygen sensor. The impedance sensor is interconnected to the output leads of the oxygen sensor and measures the impedance between them. The controller first activates and then deactivates the heater. The controller also receives the impedance signals representing the impedance of the oxygen sensor when the heater is both on and off.

Abstract: A heated exhaust gas oxygen sensor assembly that automatically detects whether the heater in the assembly is malfunctioning. The assembly includes an oxygen sensor, heater, impedance sensor, and controller. The oxygen sensor detects the relative oxygen concentration in the exhaust gas of an internal combustion engine and issues signal along a pair of output leads. The heater physically warms the oxygen sensor. The impedance sensor is interconnected to the output leads of the oxygen sensor and provides an impedance measurement to the controller. The controller compares the impedance to a predetermined threshold value to judge the effect of the heater in physically warming the sensor. If the impedance is above a predetermined threshold, the controller determines that the heater is not operating properly and issues an alarm signal.

Abstract: The invention relates to a method and an arrangement for checking the operability of an electric heater in motor vehicles and especially the heater of an oxygen probe which is mounted in the exhaust gas channel of an internal combustion engine. It is necessary to determine the temperature-dependent electrical resistance and the temperature of the oxygen probe heater for a precise evaluation of the operational state of the oxygen probe heater. The basic principle of the invention is based upon the consideration that the measurement of the electrical resistance of the oxygen probe heater is then carried out when the oxygen probe heater has cooled down to the ambient temperature. Whether this cool down has taken place can be determined in various ways in accordance with the invention, for example, from the cool down of the engine block or by a comparison of the engine block temperature to the intake-air temperature.

Abstract: In a fuel injected internal combustion engine, the fuel injection is based on computation rather than direct measurement of air intake. To correct for air intake volume changes caused by external factors, a pressure sensor detects the pressure inside the exhaust manifold and, based on this detected value, a correction is made either to the computed value for air intake, directly to the computation of the amount of fuel to be injected, or both. The corrected air intake volume and the corrected fuel injection amount are then used as the basis for ECU control of the time power is applied to the fuel injector.

Abstract: An air-fuel ratio control device comprising an O.sub.2 sensor arranged in an exhaust passage, an air-fuel ratio feedback correction amount calculating unit for calculating an air-fuel ratio feedback correction amount in accordance with an output of the O.sub.

Abstract: A air-fuel control system for internal combustion engines using a blended fuel composed of gasoline and alcohol for determining or presuming a correction factor due to alcohol concentration in the fuel when an alcohol sensor for detecting the same has failed. An average value of the O.sub.2 feedback correction factor reflecting a deviation between a target air fuel ratio and an actual air-fuel ratio is obtained and based on it, a target value is determined. The average value is compared with upper and lower limits and when it reaches either one, the factor obtained when the sensor operated properly is adjusted by an amount to follow up the target value.

Abstract: A disorder diagnosis device for a combustion engine having a fuel injector for each cylinder and a fuel system for supplying fuel to the injector comprises an air-fuel ratio sensor provided at an exhaust tube of the combustion engine for providing an air-fuel ratio signal indicative of an air-fuel ratio, and a control unit responsive to the air-fuel ratio sensor for calculating a first value by comparing the air-fuel ratio signal with a preset value and for calculating a second value by comparing a signal corresponding to the air-fuel ratio signal with a predetermined value so as to decide if the fuel system is in disorder on the basis of a combination of the first and second values.

Abstract: In an apparatus for diagnosing an abnormality in a fuel injection system in which an injection quantity is feedback-controlled by adjusting a first air-fuel ratio correction value so that an air-fuel ratio is equal to a target air-fuel ratio. The injection quantity is also adjusted by a second air-fuel ratio correction value. When the first air-fuel ratio correction value has reached a first upper limit value, the second air-fuel ratio correction value is set to a second upper limit value. When the first air-fuel ratio correction value has reached a second lower limit value, the second air-fuel ratio correction value is set to a second lower limit value. When the first air-fuel ratio correction value is outside of a predetermined range when a predetermined time has elapsed after the second air-fuel ratio correction value is set to either the second upper limit value or the second lower limit value, it is determined that a fault has occured in the fuel injection system.

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: Method and apparatus for detecting a failure of a pressure sensor provided in association with a cylinder of an internal combustion engine for detecting the pressure therein. Decision as to occurrence of a failure in the pressure sensor is made on the basis of the cylinder pressure detected by the pressure sensor through comparison with a prescribed reference value or range. Failure of the pressure sensor is determined if the detected cylinder pressure deviates from the reference value or range by a predetermined amount. Upon detection of a pressure sensor failure, an engine control parameter such as ignition timing for controlling the associated cylinder in dependence on the pressure sensor output is set to a fixed value or the operation of the cylinder is stopped.

Abstract: A method of detecting abnormality in an internal combustion engine, which is applied to at least one of a catalyst system, an evaporative fuel-purging system, a fuel supply system, an air-fuel ratio sensor, and an ignition system, for performing detection of abnormality therein according to operating parameters of the engine. An amount of residual fuel in the fuel tank is detected and the amount of residual fuel is compared with a predetermined value. The abnormality detection is inhibited when, as a result of the comparison, the amount of residual fuel is below the predetermined value.

Abstract: A method is disclosed for adjusting the amount of fuel to be supplied to an internal combustion engine in the case of non-idling operation even when the load signal fails. A plurality of emergency injection times are used which are modified with the manipulated variable of a lambda controller so that an injection time period is associated with each emergency injection time. The injection time periods are arranged such that they cover essentially all the injection times which can occur during the operation of an internal combustion engine. In the method, the lambda control remains switched on and the point at which control is to occur is found by running through the injection time periods. An arrangement for carrying out the method is also disclosed.

Abstract: Only an air-fuel ratio of one specific cylinder is forcibly shifted by the correction of the fuel supply quantity, and the fuel supply characteristic error rate of fuel supply means of this one specific cylinder, where the air-fuel ratio is forcibly shifted is detected based on whether or not the influence of this shifting of the air-fuel ratio is manifested on the air-fuel ratio feedback correction value set, based on the average air-fuel ratio in respective cylinders, as expected. Correction values of the fuel supply quantity are set separately for respective cylinders, based on the fuel supply characteristic error rates thus determined separately for respective cylinders.

Abstract: In a fuel supply control system of an internal combustion engine having a function of feedback-controlling the air-fuel ratio, dispersions of the fuel supply characteristics in respective cylinders are corrected by changes of the air-fuel ratio by the correction of the fuel supply quantity. Factors causing the deviations of the air-fuel ratio are independently compensated by learning the correction value for correcting the fuel supply quantity only at a certain ratio and the correction value for correcting the fuel supply quantity only by a certain quantity so that these correction values are commonly fit for at least two different driving conditions.