FAILURE DIAGNOSIS DEVICE FOR EXHAUST EMISSION CONTROL SYSTEM AND EXHAUST EMISSION CONTROL SYSTEM WITH FAILURE DIAGNOSIS FUNCTION

摘要

PROBLEM TO BE SOLVED: To accurately diagnose a failure of an exhaust gas flow passage change over means in an exhaust emission control system.

SOLUTION: ECU 100 of an engine system 10 can suitably change over a flow passage of an exhaust gas flowing in a catalyst device 300 between a bypass flow passage 320 and a bypassed flow passage 210a by controlling a change over control valve 340. A second temperature sensor 360 is installed in the bypass flow passage 320, and a first temperature sensor 350 is installed on an upstream side of an underfloor catalyst 310 installed on a downstream side of the bypassed flow passage 210a. High and low relation between temperature value detected by the two temperature sensors is alternated according to the selected flow passage. Also, a shape of the bypass flow passage 320 is determined to effectively create this alternation. The ECU 100 diagnoses a failure of the change over control valve 340 based on the relative relation of the two temperature values.

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