Denso Corporation

Eijirou Yamada

Yasuo Sagisaka

Yasuo Hirata

Tetsuji Mitsuda

Hirofumi Shouda

Soichi Saitoh

After an engine automatic stop processing is started, a diagnosis of a starter is started at a time of twhen an engine speed drops to a diagnosis starting speed. Before the engine speed drops to the lower limit speed at which an engine can be restarted without being cranked by the starter, the diagnosis of the starter is conducted. In the diagnosis of the starter, it is determined whether the starter is faulty based on a current passing through the starter when a relay is turned off to stop energization of the starter before the starter actually rotates after the relay is turned on. Thereby, a malfunction of the starter can be detected before the engine is automatically stopped. It is avoided to automatically stop the engine which is incapable of being automatically restarted due to the malfunction of the starter.

Diagnosis device for vehicle

An exhaust gas sensor for detecting oxygen concentration in exhaust gas is disposed in an exhaust pipe of an internal combustion engine. The sensor including a heater is controlled by a system that includes an electronic control unit. Water vapor contained in the exhaust gas is condensed on the sensor when the exhaust gas temperature is low. If the water condensation occurs while the sensor is heated by the heater, a sensor element may be cracked due to local cooling by the condensed water. To avoid the water condensation, the exhaust gas temperature is raised by retarding ignition timing of the engine for a certain period after the engine is started. After the exhaust gas is heated to a certain level, the sensor is heated. Alternatively, heating of the sensor is prohibited until the exhaust gas temperature becomes to a level at which no water condensation occurs. Thus, the cracking of the sensor element is avoided while making a delay of sensor activation minimal.

System for controlling exhaust gas sensor having heater

In a multi-cylinder engine, to compute the air-fuel ratio of each cylinder by an air-fuel ratio sensor disposed in an exhaust pipe, a cylinder is determined by a crank angle detected by a crank angle sensor. A deviation in the air-fuel ratio of each cylinder is detected on the basis of the output signal of the air-fuel ratio sensor disposed in the exhaust pipe and the forcibly changed quantity of the air-fuel ratio.

Air-fuel ratio detection apparatus of internal combustion engine

When detecting the data showing an output characteristics of an air-fuel ratio sensor, the air-fuel ratio (feed air-fuel ratio) supplied to each cylinder is alternately changed to rich or lean by a predetermined ratio (X %). And then, the average value of the detected air-fuel ratio &#x3bb; in the rich side and the lean side is respectively computed. A ratio between the variation width of the air-fuel ratio and the detection variation of the air-fuel ratio sensoris computed as an output-characteristics correction value for correcting the dispersion in the output characteristics of the air-fuel ratio sensor. By correcting the air-fuel ratio detection of the air-fuel ratio sensor with this output-characteristics correction value, the dispersion in the output characteristics due to manufacturing tolerances, aged deterioration, etc. of the air-fuel ratio sensor is corrected.

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Hekinan, Japan

Eijirou Yamada