| 摘要 |
PROBLEM TO BE SOLVED: To execute failure judgment even if atmospheric pressure is low, and inhibit wrong judgment. SOLUTION: In a system which is provided with a bypass channel 350 having HC adsorbing material 340 installed therein, a normal passage 360, the switching valve driven by negative pressure and switching a channel to one of those, and an under floor catalyst 330 installed in a downstream of a merging point of exhaust gas passages 350, 360, and which judges a failure of a switching valve 370 based on comparison of a parameter relating to exhaust temperature and predetermined threshold, the threshold is changed according to atmospheric pressure. Risk of judging imperfect operation of the switching valve 370 caused by drop of atmospheric pressure on highland as a failure can be inhibited. COPYRIGHT: (C)2008,JPO&INPIT
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