Abstract: In detecting a deterioration of an air-fuel ratio sensor, a sensor output change speed integrated value is calculated when an element temperature of a solid electrolyte is stabilized at a low temperature. Successively, a sensor output change speed integrated value is calculated when the solid electrolyte element is stabilized at a high temperature. Finally, a deviation between the change speed integrated values is calculated. By comparing the deviation amount with a predetermined determinant, presence or absence of the deterioration is determined.

Abstract: At a time point at which an ignition switch is made OFF and an engine is stopped, an output of a downstream gas sensor is read, thereafter, at a time point at which a predetermined time period has elapsed from stopping the engine, the output of the downstream gas sensor changed by flowing the atmosphere back into an exhaust pipe is read. Thereafter, a change in the output of the downstream gas sensor until the predetermined time period has elapsed from stopping the engine is calculated, the change in the output is compared with an abnormality determinant and when the change in the output is smaller than the abnormality determinant, response of the downstream gas sensor is determined to be abnormal.

Abstract: An electronic control unit of an internal combustion engine performs preheat energization control before activation energization control. In the activation energization control, a gas sensor is energized with electric power capable of heating the gas sensor to activation temperature. In the preheat energization control, the gas sensor is energized with low electric power, which is not enough to heat the gas sensor to the activation temperature. Thus, while there is a possibility that water adheres to a sensor main body of the gas sensor, the sensor main body is prevented from being heated to high temperature. Meanwhile, even if water droplets exist in the sensor main body of the gas sensor, the water is vaporized gradually, while preventing the bumping of the water.

Abstract: An engine control system has a self-diagnosis function of an exhaust system. The self-diagnosis function includes a first mode for detecting a failure or abnormality of the exhaust system as a whole, and a second mode for determining and locating a specific failed component in the exhaust system. The first mode is executed during the engine is operated under a normal condition. Therefore it is possible to detect the failure of the exhaust system without lowering a drive performance or increasing emissions. In case of detecting any failure in the first mode, the second mode is activated in response to a command signal that can be entered via a service tool. In the second mode, the engine is operated in order to determine the failed component. In the second mode, determining the failed component takes priority over keeping the drive performance or reducing emissions.

Abstract: An emission control system has a catalyst and a sensor responding to a component of exhaust gas. In order to speed warming up the catalyst, the emission control system increases the amount of heat dissipated by exhaust gas. A diagnosis of the emission control system is carried out by determining whether the amount of heat dissipated by exhaust gas is sufficient or insufficient. The amount of heat dissipated by exhaust gas is represented by the length of time to an activated state of the sensor. In the diagnosis, the amount of heat generated by a heater provided in the sensor is taken into consideration.

Abstract: A leak check system executes a leak check processing. In the leak check processing, the system closes a canister valve and a purge valve to close the fuel vapor purge system. Then, the system detects and monitors a pressure in the fuel vapor purge system. During the leak check processing, the system detects a rapid change of the pressure that is caused by a deformation of a wall of a fuel tank. The system cancels or suspends the processing to avoid erroneous detection of the leak. If the leak check is canceled, the system opens the canister valve to open the fuel vapor purge system.

Abstract: A fuel-vapor-processing system for an engine has a canister for accumulating fuel evaporation gas. The system has a leak-check apparatus for checking a leak on passages. The leak-check apparatus includes a leak-check means for carrying out leak-check processing when the engine if in a stopped state. The leak-check means operates only if a predetermined condition is satisfied. It is thus possible to reduce the number of times the leak-check processing is carried out and, hence, possible to reduce power consumption. For example, only if a relatively small leak is detected when the engine is in a running state, the leak-check processing is carried out in a stopped state to verify existence of such a leak. In the leak-check processing, the temperature of fuel, detected by a sensor or an estimated value, may be taken into consideration.

Abstract: In a fuel vapor handling system of this invention, an ECU performs a leak check to check a leak of fuel vapor in a fuel vapor passage when the engine is at a stop. The ECU functions to detect the quantity of fuel during the engine stop. The ECU detects the quantity of fuel at the time of engine starting. Furthermore, the ECU compares the quantity of fuel measured at the time of engine starting with the quantity of fuel measured at the preceding engine stop, to thereby determine whether a filler cap was opened during the engine stop. When the filler cap was opened during the engine stop, a result of the leak check will be cancelled. When the filler cap was not opened, the result of the leak check will be determined.

Abstract: A fuel vapor control system has a controller that carries out a leak check processing after the engine is stopped. The controller includes a device that intermittently activates the controller itself or a part of the controller to sample an internal pressure of the fuel vapor passage. Then, after a predetermined time, the controller determines that whether the sampled values of the internal pressure indicate a leak or not by evaluating the sampled values. According to the arrangement, since at least a part of the controller is activated intermittently, the consumption of electricity can be reduced. The fuel vapor control system has a canister valve and a purge valve made of normally close type valves in order to reduce the consumption of electricity after the engine is stopped.

Abstract: A fuel-vapor-processing system for an engine has a canister for accumulating fuel evaporation gas. The system has a leak-check apparatus for checking a leak on passages. The leak-check apparatus includes a leak-check means for carrying out leak-check processing when the engine if in a stopped state. The leak-check means operates only if a predetermined condition is satisfied. It is thus possible to reduce the number of times the leak-check processing is carried out and, hence, possible to reduce power consumption. For example, only if a relatively small leak is detected when the engine is in a running state, the leak-check processing is carried out in a stopped state to verify existence of such a leak. In the leak-check processing, the temperature of fuel, detected by a sensor or an estimated value, may be taken into consideration.

Abstract: An electronic control unit of an internal combustion engine performs preheat energization control before activation energization control. In the activation energization control, a gas sensor is energized with electric power capable of heating the gas sensor to activation temperature. In the preheat energization control, the gas sensor is energized with low electric power, which is not enough to heat the gas sensor to the activation temperature. Thus, while there is a possibility that water adheres to a sensor main body of the gas sensor, the sensor main body is prevented from being heated to high temperature. Meanwhile, even if water droplets exist in the sensor main body of the gas sensor, the water is vaporized gradually, while preventing the bumping of the water.

Abstract: In detecting a deterioration of an air-fuel ratio sensor, a sensor output change speed integrated value is calculated when an element temperature of a solid electrolyte is stabilized at a low temperature. Successively, a sensor output change speed integrated value is calculated when the solid electrolyte element is stabilized at a high temperature. Finally, a deviation between the change speed integrated values is calculated. By comparing the deviation amount with a predetermined determinant, presence or absence of the deterioration is determined.

Abstract: An engine control system has a self-diagnosis function of an exhaust system. The self-diagnosis function includes a first mode for detecting a failure or abnormality of the exhaust system as a whole, and a second mode for determining and locating a specific failed component in the exhaust system. The first mode is executed during the engine is operated under a normal condition. Therefore it is possible to detect the failure of the exhaust system without lowering a drive performance or increasing emissions. In case of detecting any failure in the first mode, the second mode is activated in response to a command signal that can be entered via a service tool. In the second mode, the engine is operated in order to determine the failed component. In the second mode, determining the failed component takes priority over keeping the drive performance or reducing emissions.

Abstract: At a time point at which an ignition switch is made OFF and an engine is stopped, an output of a downstream gas sensor is read, thereafter, at a time point at which a predetermined time period has elapsed from stopping the engine, the output of the downstream gas sensor changed by flowing the atmosphere back into an exhaust pipe is read. Thereafter, a change in the output of the downstream gas sensor until the predetermined time period has elapsed from stopping the engine is calculated, the change in the output is compared with an abnormality determinant and when the change in the output is smaller than the abnormality determinant, response of the downstream gas sensor is determined to be abnormal.

Abstract: In a fuel vapor handling system of this invention, an ECU performs a leak check to check a leak of fuel vapor in a fuel vapor passage when the engine is at a stop. The ECU functions to detect the quantity of fuel during the engine stop. The ECU detects the quantity of fuel at the time of engine starting. Furthermore, the ECU compares the quantity of fuel measured at the time of engine starting with the quantity of fuel measured at the preceding engine stop, to thereby determine whether a filler cap was opened during the engine stop. When the filler cap was opened during the engine stop, a result of the leak check will be cancelled. When the filler cap was not opened, the result of the leak check will be determined.

Abstract: An emission control system has a catalyst and a sensor responding to a component of exhaust gas. In order to speed warming up the catalyst, the emission control system increases the amount of heat dissipated by exhaust gas. A diagnosis of the emission control system is carried out by determining whether the amount of heat dissipated by exhaust gas is sufficient or insufficient. The amount of heat dissipated by exhaust gas is represented by the length of time to an activated state of the sensor. In the diagnosis, the amount of heat generated by a heater provided in the sensor is taken into consideration. The diagnosis can also be carried out before and after the warming up the catalyst. The heater can also be deactivated. Detection of an abnormality of a secondary air control system can be based on a component of exhaust gas. If the amount of heat dissipated by exhaust gas is found insufficient, additional control can be executed.

Abstract: A leak check system executes a leak check processing. In the leak check processing, the system closes a canister valve and a purge valve to close the fuel vapor purge system. Then, the system detects and monitors a pressure in the fuel vapor purge system. During the leak check processing, the system detects a rapid change of the pressure that is caused by a deformation of a wall of a fuel tank. The system cancels or suspends the processing to avoid erroneous detection of the leak. If the leak check is canceled, the system opens the canister valve to open the fuel vapor purge system.

Abstract: A fuel vapor control system has a controller that carries out a leak check processing after the engine is stopped. The controller includes a device that intermittently activates the controller itself or a part of the controller to sample an internal pressure of the fuel vapor passage. Then, after a predetermined time, the controller determines that whether the sampled values of the internal pressure indicate a leak or not by evaluating the sampled values. According to the arrangement, since at least a part of the controller is activated intermittently, the consumption of electricity can be reduced. The fuel vapor control system has a canister valve and a purge valve made of normally close type valves in order to reduce the consumption of electricity after the engine is stopped.

Abstract: A fuel vapor control system has a controller that carries out a leak check processing after the engine is stopped. The controller includes a device that intermittently activates the controller itself or a part of the controller to sample an internal pressure of the fuel vapor passage. Then, after a predetermined time, the controller determines that whether the sampled values of the internal pressure indicate a leak or not by evaluating the sampled values. According to the arrangement, since at least a part of the controller is activated intermittently, the consumption of electricity can be reduced. The fuel vapor control system has a canister valve and a purge valve made of normally close type valves in order to reduce the consumption of electricity after the engine is stopped.

Abstract: A leak check system executes a leak check processing. In the leak check processing, the system closes a canister valve and a purge valve to close the fuel vapor purge system. Then, the system detects and monitors a pressure in the fuel vapor purge system. During the leak check processing, the system detects a rapid change of the pressure that is caused by a deformation of a wall of a fuel tank. The system cancels or suspends the processing to avoid erroneous detection of the leak. If the leak check is canceled, the system opens the canister valve to open the fuel vapor purge system.