Abstract: A control device detects a characteristic change of an air-fuel ratio sensor indicative of deterioration of the air-fuel ratio sensor. The control device determines deterioration due to aging of the air-fuel ratio sensor accurately and calculates an air-fuel ratio from the air-fuel ratio sensor highly accurately. Then, the control device detects a current proportional to the concentration of oxygen in the detected gas from a sensor element by applying a voltage to the sensor element of the air-fuel ratio sensor. By applying AC voltages at high and low frequencies to the element, an AC impedance is detected. The temperature of the element is controlled to a target temperature according to the high frequency impedance and a characteristic change of the element is detected in accordance with the low frequency impedance.

Abstract: A control arrangement for an internal combustion engine which includes a fuel supply system, an air/fuel ratio control system, an abnormality diagnoser which diagnoses a possible abnormality in the fuel supply system, when the pressure of the pressurized fuel in the fuel supply system detected by a fuel pressure senor exceeds predetermined upper and lower limits determined by a control duty for an electrically controlled pressure regulator, and an abnormal element decider which decides an abnormality either in the fuel pressure sensor or in the electrically controlled pressure regulator based on an amount representing an air/fuel ratio status including the actual air/fuel ratio and the air/fuel ratio feed back control amount extracted from the air/fuel ratio control system for the internal combustion engine, when the abnormality diagnoser diagnoses an abnormality in the fuel supply system.

Abstract: There is provided an apparatus for determining a failure of an oxygen concentration sensor, which is capable of determining a failure of the oxygen concentration sensor accurately and promptly. The oxygen concentration sensor 25 is arranged at a location downstream of a catalyst 8 in an exhaust system of an internal combustion engine 3. The apparatus 1 measures a time period elapsed after termination of a fuel cut-off operation, and calculates an integrated amount SUMSVS of exhaust gases exhausted after the termination of the fuel cut-off operation (step S13). A failure of the oxygen concentration sensor is determined depending on whether or not a signal value SVO2 of a signal from the oxygen concentration sensor 25 has crossed a predetermined threshold value #SVO2CHK (steps S51, 55).

Abstract: A compressed natural gas-fueled automotive vehicle is disclosed in which the fail-safe control operation is performed thereby to secure the safety of the vehicle when the gas pressure drops. If the remaining amount of the gas is very small, an engine misfire occurs. If the catalyst temperature is high, the uncombusted gas begins to burn on contact with the high-temperature catalyst in the catalyst unit. In view of this, upon detection of both a gas pressure drop and the vehicle moving condition or upon detection of both a gas pressure drop and an increased catalyst temperature, the fuel supply is stopped or the vehicle speed is reduced to thereby reduce the catalyst temperature. As a result, uncombusted gas is not burnt in the catalyst unit and the catalyst unit is prevented from being destroyed.

Abstract: An estimated value of the amount of fuel which is metered into a cylinder per working cycle is calculated. An estimated value of the indicated torque of the internal combustion engine is calculated as a function of the estimated value of the amount of fuel. An emergency operating mode of the internal combustion engine is actuated if the estimated value and a setpoint value of the indicated torque fulfill a predefined condition.

Abstract: A system for controlling an in-cylinder fuel injection engine determines that a high-pressure fuel system is abnormal, when meeting at least one of conditions that the fuel pressure Pf of the high-pressure fuel system does not reach a preset pressure PFS (S24) even if a predetermined period of time elapses after the engine start-up (S22), that the fuel pressure Pf of the high-pressure fuel system is not within an ordinary fuel pressure range defined by the lower limit PFL and the upper limit PFH after the engine start-up (S27, S28), and that the fuel injection pulse width Ti continues to exceed the upper limit TiNGMAX, which can not usually be obtained, for a predetermined period of time at a lean air-fuel ratio (S30.about.S33). Thus, the abnormality of the high-pressure fuel system of the in-cylinder fuel injection engine can be accurately diagnosed.

Abstract: An air-fuel ratio sensor system is diagnosed for the presence/absence of an abnormality on the basis of a reference voltage appearing at one end of a current detecting resistor and a detection voltage appearing at the other end of the current detecting resistor for detecting a current output by an air-fuel ratio sensor. If the reference voltage is outside a normal range and higher than the detection voltage, the air-fuel ratio sensor system is determined to be in a rich abnormality. If the reference voltage Vafon is outside the normal range and lower than the detection voltage, the air-fuel ratio sensor system is determined to be in a lean abnormality. If the reference voltage is within the normal range and a state of the detection voltage being close to a power supply voltage has been continuing for a predetermined period of time, the air-fuel ratio sensor system is determined to be in a circuit-shorting.

Abstract: A control system for a plant includes a sensor for detecting an output from the plant, an adaptive controller for controlling a manipulated variable applied to control of the plant in such a manner that an output from the sensor becomes equal to a desired value, and an adaptive parameter-adjusting device for adjusting adaptive parameters used by the adaptive controller. The adaptive parameter-adjusting device has an identification error-calculating device for calculating an identification error of the adaptive parameters and generating an identification error signal indicative of the calculated identification error, and an adjusting device for adjusting the adaptive parameters based on the calculated identification error. The adaptive parameter-adjusting device includes a non-linear filter for generating an output of 0 or approximately 0 in response to the identification error signal when the identification error is within a predetermined range.

Abstract: An engine fuel supply apparatus is provided with an accident judging device for effecting accident judgement in a fuel control system under the conditions that the fuel pressure regulator driver is subjected to feedback control of the fuel pressure, and that there is a change in the fuel pressure and the change continues for a predetermined time of period within a set time range.

Abstract: An engine diagnostic method for an engine having a switching exhaust gas sensor and a fuel system uses the switching exhaust gas sensor during open loop fuel enrichment to diagnose fuel system degradation, including fuel filter degradation.

Abstract: A defect recognition device is provided for internal-combustion engines, as well as a process for operating an internal-combustion engine having at least two exhaust gas trains, with one lambda probe respectively being in each exhaust gas train. A joint measuring device detects the supplied air and a joint timing device apportions the fuel. The lambda probes, which generate a continuous signal for the lambda value of the exhaust gas, are used to provide improved defect recognition. The defect recognition device recognizes a defect when the signals supplied by the lambda probes deviate from one another.

Abstract: Internal combustion engine air/fuel ratio control responsive to low voltage operating conditions of an electrical system maintains stable, precise air/fuel ratio conditions under electrical system fault conditions affecting operation of fuel control components including fuel pumps, fuel injectors, and drivers therefor. Electrical system operating voltage is monitored and when a voltage drop below a voltage threshold associated with reliable engine cylinder air/fuel ratio control is diagnosed, the air/fuel ratio smoothly transitions to a reduced engine performance operating mode which, at least for high engine output power requests, limits fueling and airflow to the engine cylinders to a level that may be accurately, reliably supported by the fuel control system components under their reduced electric drive signals. The reduced performance operating mode is maintained while the fault condition persists.

Abstract: A diagnostic system for a fuel system of an internal combustion engine such as direct-injection gasoline engine monitors a pressure deviation of a actual fuel pressure sensed by a fuel pressure sensor from a desired fuel pressure in a feedback fuel pressure control, and thereby detects abnormality in the fuel system. When the pressure deviation continues to be outside a normal range, a diagnostic controller commands engine operation in a homogeneous stoichiometric combustion mode, and monitors a feedback correction quantity in a feedback stoichiometric air fuel control during the engine operation in the homogeneous stoichiometric combustion mode. The controller attributes the abnormality to the fuel pressure sensor if the feedback correction quantity of the air fuel ratio is fixed to an upper limit or a lower limit.

Abstract: The invention is directed to a method for monitoring the operation of a gas probe, such as a .lambda.-probe for an internal combustion engine. The .lambda.-probe has a probe ceramic (Nernst cell) and a probe heater. The internal resistance (x) of the probe ceramic is measured and a desired value (y) is determined in dependence upon the temperature of the gas to be detected and the heating power of the probe heater. The internal resistance (x) is then compared to the desired value (y) and, when the measured value of the internal resistance (x) exceeds the desired value (y), then a fault signal is generated and/or the fault signal is outputted and/or the fault signal is stored.

Abstract: When fuel supply system abnormality diagnosis conditions are satisfied, the abnormality of a fuel supply system is diagnosed by comparing an air/fuel ratio deviation index value with a lean/rich abnormality determination value by diagnosis means. At this time, a hot lean abnormality determination value KHL is set leaner than an ordinary lean abnormality determination value KLL, and a hot rich abnormality determination value KHH is set richer than an ordinary rich abnormality determination value KLH by abnormality determination value setting means when the engine compartment temperature is high. As a result, it is possible to diagnose whether or not the fuel supply system is abnormal (i.e., an abnormal deviation in the air/fuel ratio) while preventing the mistake even when the engine compartment temperature is high, so that the early discovery of the abnormality and the prevention of the mistaken diagnosis are made compatible.

Abstract: The invention is directed to a method of checking a pressure sensor of a fuel supply system of an internal combustion engine such as an engine for a motor vehicle. The fuel supply system includes a pressure store to which fuel is supplied and a pressure sensor for measuring the pressure in the pressure store. Fuel is supplied from the pressure store to a combustion in the engine and the pressure in the pressure store is changed. The behavior of the combustion of the fuel is detected and a conclusion is drawn as to the operability of the pressure sensor from the detected behavior of the combustion.

Abstract: An oxygen concentration detecting apparatus precisely and easily performs diagnosis of a limit current type oxygen sensor. The limit current type oxygen sensor has an oxygen concentration detecting element for outputting limit current proportional to the oxygen concentration and a heater for heating the detecting element. A CPU of a microcomputer controls energization of the heater to activate the oxygen sensor. The CPU calculates element resistance based on the voltage applied to the oxygen sensor and the current detected in the sensor. In a sensor diagnosis routine, the CPU determines whether preconditions for the diagnosis have been met. If all the preconditions have been met, the CPU executes the diagnosis. That is, the CPU determines whether the element resistance is within a predetermined range. If it is below the range, the CPU determines that the sensor has high element temperature abnormality.

Abstract: In an engine fuel supply system, the difference between the actual and target air-fuel ratios, an air-fuel ratio feedback correction coefficient and a learned correction amount are added as a parameter for diagnosing the fuel supply system. The diagnostic parameter is smoothed and the smoothed value is compared with a diagnosis reference value, thereby detecting a malfunction in the fuel supply system. Even if the learned correction amount is not updated, the malfunction in the fuel supply system can be promptly detected from the difference between the actual and target air-fuel ratios and the air-fuel ratio correction coefficient. The diagnosis reference value is determined variably in accordance with engine operating parameters such as the amount of intake air.

Abstract: The present invention provides a method of compensating for an erroring sensor in a flexible fuel compensation control system for a flexible fueled vehicle. The methodology provides a method for identifying preselected operating conditions without the output of the erroring sensor. As such, the flexible fuel compensation control system may still be employed to ensure vehicle drivability even in the absence of input from an erroring sensor.

Abstract: An engine control system and method that utilizes throttle position as one of its control parameters. The throttle position sensor is checked by sensing changed values in a time period when the engine is operating within a predetermined speed range during which changes in throttle position are not normally encountered.

Abstract: A device for determining deterioration of an air-fuel ratio sensor according to the present invention includes: an air-fuel ratio sensor provided in an exhaust passage of an internal combustion engine, the air-fuel ratio sensor being capable of continuously detecting a broad range of air-fuel ratios including a stoichiometric air-fuel ratio; an air-fuel ratio feedback control circuit for feedback controlling a fuel injection amount based on a difference between an output of the air-fuel ratio sensor and a target output corresponding to a target air-fuel ratio so that an air-fuel ratio of a gaseous mixture substantially equals the target air-fuel ratio, the gaseous mixture being supplied to the engine; a variation cumulative value calculation circuit for cumulating, while the air-fuel ratio feedback control is being performed by the air-fuel ratio feedback control circuit, a variation .DELTA.FT in a fuel injection correction amount, thereby calculating a cumulative variation value .SIGMA..DELTA.

Abstract: A control apparatus of an internal combustion engine includes an electronic control unit which determines whether a throttle valve opening sensor is normal or faulty in accordance with an output from the sensor. If the throttle valve opening sensor operates normally, a target air-fuel ratio is set in accordance with the output of the sensor. On the other hand, if the throttle valve opening sensor is in trouble, the control unit sets the target air-fuel ratio to a ratio equal to or close to the stoichiometric air-fuel ratio in accordance with the output of an intake air amount sensor, whereby a stable operation of the internal combustion engine is ensured.

Abstract: The present invention relates to a process for controlling the proper operation of an air-assisted injector (17) during the start-up phase of an internal combustion engine (11). This injector is adapted to deliver a predetermined quantity of fuel to the engine. The process according to the invention is characterized in that it comprises:a verification a posteriori, during a stabilized idle phase, that a predetermined quantity of air can be injected during the air assistance phase.The present invention also relates to a device which implements this process and is particularly applicable to the field of automotive electronics.

Abstract: A system for controlling fuel metering for an internal combustion engine having a feedback system which has a controller for calculating a feedback correction coefficient, using an adaptive control law to correct a quantity of fuel injection such that a detected air/fuel ratio is brought to a desired air/fuel ratio. In the system, it is discriminated whether the feedback correction coefficient and the detected air/fuel ratio are in phase, and the feedback system is instable when they are discriminated to be in phase. Since the coefficient acts to correct the deviation of the detected air/fuel ratio from the desired air/fuel ratio, they are normally in antiphase. It is thus possible to find the system instable, by discriminating whether they are in phase or not.

Abstract: The invention is directed to a method of detecting and documenting exhaust-gas relevant malfunctions of a vehicle equipped with an internal combustion engine utilizing onboard equipment. Malfunctions are detected by a sensor device and evaluated in a circuit unit. The malfunction is displayed by a warning lamp (fault announcement) and is stored in a fault memory. A pressure measurement in the fuel loop is made and the output as well as the storage of the fault announcement is made in dependence upon the measured pressure. This is done to differentiate fault announcements based on a fuel tank run to empty.

Abstract: Fuel is pressurized by the expansion and contraction of a pump chamber defined inside a casing according to the rotation of a power input shaft which penetrates from the outside of the casing into its inside. A first seal member is provided between the casing and the power input shaft and prevents escape of fuel which is inside the casing, and a second seal member is provided in series therewith. Further, leakage of fuel to the outside of the casing from the second seal member is prevented by the provision of a drain conduit which drains fuel which has leaked into a space defined between the first seal member and the second seal member.

Abstract: A method and system for monitoring fuel delivery to an internal combustion engine having a first and second mode of operation and controlling the engine accordingly. An oxygen content of exhaust gas emitted from the engine is sensed and a corresponding oxygen content signal is generated. Air fuel ratio correction data is determined based on the oxygen content signal. If the engine is operating in the first mode, the air fuel ratio correction data is compared to a first set of predetermined air fuel ratio correction thresholds and a first failure signal is generated based on the comparison between the air fuel ratio correction data and the first set of predetermined air fuel ratio correction thresholds.

Abstract: An internal combustion engine has a system, including diagnostics, for providing oxygen enriched air so as to control emissions of unburned hydrocarbons and carbon monoxide. The system includes the capability of determining whether the oxygen enrichment system is providing suitable mass flow to the engine and whether oxygen enrichment is available according to the specifications of the enrichment device.

Abstract: An air-fuel ratio control system which calculates a basic injection amount of fuel by state detecting sensors (21) each of which detects an operating state of an internal combustion engine, air-amount detecting sensors (22) each of which detects an intake air amount, an air-fuel ratio sensor (23), and a predetermined data group. Further, the air-fuel ratio control system stores past amount data of injected fuel and air-fuel ratio data at each control cycle. A neuro-computation unit (29) reads values of the data detected by the sensors (21,22) and the stored data to obtain an air-fuel ratio estimate to calculate a correction injection amount of fuel by a neural network of a forward neuro-computing unit (210), which has learned beforehand about relations of the injected fuel amount, the detected air-fuel ratio, parameters, and dead time.

Abstract: In the present invention, the fuel injection amount of the engine is determined by an air-fuel ratio feedback correction factor FAF and a feedback learning correction factor KG and a fuel vapor learning correction factor FGPG. When the fuel vapor is supplied to the engine, the value of FGPG is adjusted so that the center value of the fluctuation of FAF agrees with 1.0 while the value of KG is held at the value before the fuel vapor supply started. On the other hand, when the fuel vapor is not supplied to the engine, the value of KG is adjusted so that the center value of the fluctuation of FAF agrees with 1.0 while the value of FGPG is set at 0. Therefore, the value (FAF+KG) indicates whether a failure has occurred in the fuel supply system regardless of the fuel vapor supply to the engine. Further, if the value (FAF+KG) becomes larger than or smaller than a predetermined range when the fuel vapor is supplied to the engine, i.e.

Abstract: A fuel injection apparatus for internal combustion engine of this invention applies detection output of a wide-range air/fuel ratio sensor to an observer so as to estimate an air/fuel ratio of individual cylinder and, based on thus estimated air/fuel ratio, obtains an air/fuel ratio correction coefficient for individual cylinder and correctively controls the fuel injection amount for individual cylinder with the air/fuel ratio correction coefficient for individual cylinder. While the estimation processing of the observer is always continued, the air/fuel ratio correction coefficient for individual cylinder is automatically adjusted, for example, when the estimated air/fuel ratio becomes an abnormal value, according to operational condition of the internal combustion engine, and the like, thereby securing the stability in the corrective control and preventing the emission from deteriorating.

Abstract: An air fuel ratio control system is so arranged to restrain a undesired variation of an air fuel ratio due to an on off control of a canister purge and thereby prevent deterioration of an exhaust performance. When a purge cut valve is closed to cut off the canister purge, the control system changes a feedback air fuel ratio corrective factor ALPHA like a step change to a predetermined initial value EVALP# to meet a leaning change of the air fuel ratio caused by the purge cut. When the purge cut valve is opened to resume the canister purge, the control system meets an enriching change of the air fuel ratio caused by restarting of the purge by producing a step change in the corrective factor ALPHA to an initial value EALPHA.times.KEVAL# determined in accordance with a value EALPHA of the corrective factor ALPHA obtained immediately before the cutoff (KEVAL# is a constant).

Abstract: A device for detecting abnormality of the fuel supply system of an internal combustion engine inhibits supply of evaporative fuel to the intake passage when the air-fuel ratio correction coefficient becomes smaller than a predetermined value, and thereafter determines that the fuel supply system is normal when the air-fuel ratio correction coefficient increases above the predetermined value as a result of the inhibition of the supply of the evaporative fuel. The supply of the evaporative fuel to the intake passage is resumed after the determination that the fuel supply system is normal has been made. Determination of abnormality of the fuel supply system is inhibited after resuming of the supply of the evaporative fuel until the engine enters a predetermined operating condition in which the air-fuel ratio correction coefficient has increased.

Abstract: An evaporative emission control system for an internal combustion engine has a purge control valve arranged in a purging passage connecting between a canister and an intake passage of the engine. The evaporative emission control system has a self-diagnosis function of determining whether the evaporative fuel emission control system is normal or abnormal from a change in a value of a parameter measured based on an output from an exhaust gas component concentration sensor arranged in an exhaust passage of the engine, which change is detected when the opening of the purge control value is changed, and a variation in pressure within the intake passage at a location downstream of a throttle valve arranged therein when the opening of the purge control valve is changed.

Abstract: A system, capable of determining an engine abnormality, is disclosed. The engine includes a first regulator for controlling air fuel ratio and a second regulator for controlling the purging amount of fuel vapor into an air-intake passage from a fuel tank. The variance in the purging amount effects the air fuel ratio. An engine control unit computes a parameter value used to control the air fuel ratio based on a signal from a detector which detects the operational condition of the engine, and controls the first regulator with the computed parameter value to allow the operational condition of the engine to approach a requested condition. A determining apparatus determines that an abnormality has occurred in the engine when the parameter value computed by the control unit continuously deviates from a predetermined numerical range for a predetermined period of time.

Abstract: A diagnostic apparatus applied to internal combustion engine exhaust gas sensors employing electrochemical polarographic principles indicates sensor operation relative to a current limiting operating region in which a sensor output signal indicates oxygen concentration in the exhaust gas. A sensor drive signal is controllably perturbed and sensor sensitivity monitored by monitoring the sensor response to the perturbation. Current limiting operation may be diagnosed and indicated when the sensor response indicates an insensitivity to the perturbation.

Abstract: A system 10 for controlling the operation of a propane powered vehicle engine includes a gas sensor 28 for providing a fuel rich signal and a fuel lean signal to a controller 20. The controller is also responsive to a tachometer 26 which senses the engine rpm. When the engine speed is in excess of a preselected value and is not decelerating, the controller generates an unacceptable engine operation signal if the period of duration of the fuel rich signal exceeds a preselected value. A warning unit 32 is provided for alerting the operator of a service required signal from the controller. A fuel shutoff device 30 automatically terminates the fuel supply to the engine in response to a fuel shutoff signal from the controller. The method of the invention allows for vehicle startup after the fuel shutoff device has been activated. The invention is particularly well suited for requiring a propane powered vehicle engine to output an acceptable level of carbon monoxide in the exhaust gas.

Abstract: A malfunction detecting system for an internal combustion engine utilizes an air/fuel ratio feedback control loop. Namely, feedback factors #nKLAF operate to absorb the air/fuel ratio variance between cylinders and to converge the individual cylinders' air/fuel ratios to the confluence point air/fuel ratio, while another feedback factor KLAF operates to converge the confluence point air/fuel ratio to a desired air/fuel ratio, converging all cylinders' air/fuel ratios to the desired air/fuel ratio. With this arrangement, any of the feedback factors #nKLAF for a certain cylinder becomes a prescribed value, it can therefore be assumed that any abnormality would occur in a part such as the fuel injector which would affect the air/fuel ratio in the cylinder concerned.

Abstract: In a control system for controlling the occurrence of an abnormality in one of the computers mounted on a motor vehicle, a decision is made based upon whether a sub CPU has been reset. In the case where the sub CPU is reset by an abnormality or a malfunction, a failsafe mode flag is set and control data are transmitted again from the main CPU to the sub CPU. The interruption is finished after the control command signal is transmitted to the sub CPU. At this time, if the failsafe mode flag is set, the failsafe control is executed. If the failsafe mode flag is not set, the normal control is executed. Therefore, even if the control data in the RAM of the computers are destroyed by the occurrence of an abnormality or malfunction, the system can regain normal operation immediately.

Abstract: With an electronic control device for an internal combustion engine using an oxygenated compound mixed fuel, operating conditions of the engine are detected, and are utilized to determine fundamental control data for the engine, while the dielectric constant and the refractive index of an oxygenated compound mixed fuel supplied to the engine are detected, and the oxygenated compound content of the mixed fuel is calculated according to the dielectric constant thus detected. The refractive index, and the oxygenated compound content are utilized to estimate the distillation characteristic of the petroleum refined fuel in the mixed fuel. The fundamental control data are corrected by using first correction data determined from the oxygenated compound content and second correction data determined from the distillation characteristic.

Abstract: An evaporative fuel-processing system for an internal combustion engine includes a charging passage extending between the canister and the fuel tank of the engine, a purging passage extending between the canister and the intake system of the engine, an open-to-atmosphere passage for communicating the interior of the canister to the atmosphere, a first control valve for selectively opening and closing the purging passage, and a second control valve for selectively opening and closing the open-to-atmosphere passage. A tank internal pressure sensor detects pressure within the evaporative fuel-processing system, and an ECU determines abnormality of the evaporative fuel-processing system, based on a variation in the detected pressure after the interior of the evaporative fuel-processing system is negatively pressurized into a predetermined negative pressure state.

Abstract: Malfunction of a purge air control system is checked based on a variation of a fuel tank inner pressure or an air-fuel ratio in response to forced introduction of purge air into an engine. During a mode of checking malfunction of the purge air control system, failure/malfunction checks on other exhaust gas control components/systems, such an ignition system, an O.sub.2 sensor and a fuel supply system, are prohibited.

Abstract: A method for distinguishing sources of error in a mixture formation or mixture regulating system of an internal combustion engine having an exhaust system with a lambda regulator and a heated lambda sensor is disclosed. A value of a sensor voltage is continuously measured. The value of the sensor voltage is compared with a lower diagnostic limit value and an upper diagnostic limit value. A lambda regulator value of the lambda regulator is varied in an enriching direction to a maximum lambda regulation limit if the lower diagnostic limit value fails to be attained, and the lambda regulator value is varied in a leaning down direction to a minimum lambda regulation limit if the upper diagnostic limit value is exceeded.

Abstract: An air-fuel ratio control apparatus of an internal combustion engine in which a canister to adsorb and hold evaporated fuel is provided in a supply passage which communicates an intake passage of the internal combustion engine and a fuel tank, and an atmosphere opening/closing valve is provided so as to open the canister to the atmosphere. A purge valve is provided in the supply passage between the intake passage and the canister, and a pressure sensor communicates with the supply passage between the canister and the fuel tank. A control that closes the atmosphere opening/closing valve is closed when leakage is judged and reduces a pressure in the fuel tank to a predetermined negative pressure value, and thereafter closes the purge valve so that a leakage state of an evaporating system is discriminated.

Abstract: In a method for assessing the operating capacity of a lambda control, which outputs regulated values FR which are to fluctuate about a desired regulated value FR.sub.- DES, which lambda control is assisted by an adaptation outputting adaptation values, the current value of a decision quantity, which indicates the averaged absolute value of deviation of the regulated value from the desired regulated value, is calculated continuously, then the current value is compared with a decision-quantity threshold value SW.sub.- EW, and the faulty signal is output when the current value exceeds the decision-quantity threshold value. It is therefore also possible to recognize those fails which occur only in part ranges of the total range in which an internal-combustion engine, in which the fuel supply is set by means of the lambda control, can be operated.

Abstract: A method is provided for checking the function of a fuel composition sensor and for learning the percent alcohol content of a fuel used in a motor vehicle capable of operating on more than one type of fuel, as an alternative to a fuel composition sensor. The present invention improves the reliability of a motor vehicle utilizing a fuel composition sensor by allowing vehicle operation to continue uninterrupted, such as when a short or open condition exists within the sensor. The method first determines whether conditions are such that the percent alcohol content of a fuel should be "learned". If conditions are appropriated, then necessary engine operating conditions are first initialized. The oxygen sensor output signal is checked to determine whether the engine is operating too rich or lean. The value of percent alcohol content stored in the engine control unit's memory is modified in the direction of stoichiometric engine operation.

Abstract: In a fuel injection system for a vehicle engine, the fuel injection is controlled in a feedback mode when no abnormality occurs in the control system, and it is controlled in an open loop mode by a limp home circuit when any abnormality in the control system is detected by a watch dog timer. The vehicle may thus be slowly driven to a safe or proper place for servicing. The limp home circuit includes fuel cutoff means for interrupting the fuel supply to the engine in the open loop mode of operation when the rotational speed of the engine exceeds a predetermined value.

Abstract: A system for monitoring suction leakage of external air into the exhaust gas path of an internal combustion engine during intermittent reduced pressure phases of the engine, during operation, includes an oxygen concentration sensing lambda probe arranged in the path. The probe issues an output signal having a reduced pressure phase pulsation frequency component of reduced pressure phase amplitude indicative of such oxygen concentration during the reduced pressure phases. The output signal is fed to a control device which generates an error signal when that amplitude exceeds a predetermined threshold level indicative of suction entry of external air into the path during a reduced pressure phase.

Abstract: An apparatus and method for self diagnosing a plurality of engine component operation controlling systems applicable to an internal combustion engine in which when predetermined diagnostic conditions to start respective self diagnoses are simultaneously established for the respective engine component operation controlling systems, one of the self diagnoses having a higher priority is executed.

Abstract: A failure diagnosis device for determining engine abnormalities by comparing the air-fuel ratio or the exhaust pressure of an engine with a predetermined value or by determining that the air fuel ratio or the exhaust pressure of the engine is different from the average air-fuel ratio or the average exhaust pressure by a predetermined amount. This comparison is made only when the engine is in a predetermined running condition in which either the air-fuel ratio or the exhaust pressure is stabilized for a predetermined period of time. When the air-fuel ratio or exhaust pressure is different from the average air-fuel ratio or from the average exhaust pressure by a predetermined value, engine abnormality can be detected for each cylinder or for each cylinder group.