Abstract: A cooling device for an engine including a radiator circulation flow channel, a heater circulation flow channel, a bypass circulation flow channel, a valve, and a pump. The channels merge in the thermostat and form a common flow channel between the thermostat and the engine. The pump is provided in the common flow channel. At a start of a warm-up period and during the warm-up operation, circulation is substantially stopped by the thermostat, cooling water circulation is actuated in the bypass circulation flow channel, and an opening degree of the electronically controlled valve is gradually increased from a minimum as the cooling water temperature rises. The electronically controlled valve is not completely closed even when closed, and is open to a certain degree from an initial stage of the warm-up period, thereby causing part of the cooling water to flow in the bypass circulation flow channel.

Abstract: A cooling device for an engine that can raise the temperature of cooling water within a short period of time during the warm-up operation and allows a simple structure. The cooling device has a radiator circulation flow channel for circulation via an engine, a radiator, and a thermostat; a heater circulation flow channel for circulation via the engine, a heater core, and the thermostat; a bypass circulation flow channel for circulation via the engine and the thermostat; an electronically controlled valve; and a pump. The radiator circulation flow channel, heater circulation flow channel, and bypass circulation flow channel merge in the thermostat and form a common flow channel between the thermostat and the engine. The pump is provided in the common flow channel.

Abstract: A diagnosis system for a wide-range A/F sensor receives an air-fuel ratio (A/F) of air-fuel mixture supplied to an engine for the A/F sensor. An control unit of the diagnosis system corrects an A/F controlled object of a feedback control on the basis of a detection result of the A/F sensor to adjust the A/F at a target A/F. The control unit diagnoses an abnormality of the A/F sensor from variation of the detection value of the A/F sensor during a time period from the start of the switching of the target A/F. The control unit sets a control gain of an A/F feedback control at a value greater than a normal control gain during the diagnosis.

Abstract: A diagnostic apparatus for supplying an assist air in an internal combustion engine includes: an assist air passage for guiding intake air from upstream of a throttle valve to a fuel injector installed downstream of said throttle valve; an assist air control valve installed in said assist air passage; a sensor for detecting an engine operating parameter; and a control unit. The control unit includes a data storage portion and a data processing portion. The control unit selectively forces the assist air control valve open and closed upon detection of at least one predetermined diagnosis condition. The control unit then calculates and stores a plurality of values corresponding to changes in the engine operating parameter based on signals received from the sensor, and determines an occurrence of an error with assist air supply based on comparisons of said values with a predetermined value.