Denso Corporation

Nobuhiro Takano

Hideyuki Ohashi

Shinichi Ito

An ECU drives a pump in a first stage at a first pumping capacity. The ECU drives the pump in a second stage after the first stage at a second pumping capacity, which is lower than the first pumping capacity. The second pumping capacity is set such that when at least one leak hole, which forms a predetermined total opening cross sectional area, exists in the purge apparatus, the driving of the pump at the second pumping capacity substantially maintains a predetermined reference pressure in the purge apparatus. The ECU diagnoses whether a leak hole exits in the purge apparatus based on the pressure measured with the pressure sensor in view of the predetermined reference pressure at the time of driving the pump in the second stage at the second pumping capacity.

Leak diagnosis system and leak diagnosis method

When transistors are switching-controlled by a microcomputer, on the basis of the absolute value of a value obtained by subtracting an actual opening angle value from an instruction value generated from the microcomputer for the opening angle of a throttle valve serving as a driven apparatus which is driven by a d.c. motor, a current flowing through each of resistors detected by comparators, and voltages at both ends of a resistor detected via each of the buffers, the microcomputer determines an abnormality in the d.c. motor and the throttle valve and an abnormality in the transistors or the power supply path while distinguishing those from each other.

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Gifu, Japan

Nobuhiro Takano