| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide technology accurately diagnosing deterioration of a catalyst while recirculating EGR gas. <P>SOLUTION: When deterioration of a catalyst unit disposed in an exhaust gas passage of the internal combustion engine and purifying exhaust gas is diagnosed, at first, part of exhaust gas from the exhaust gas passage is taken in as EGR gas, EGR gas recirculation using an EGR device recirculating the EGR gas to an intake air passage of the internal combustion engine is stopped once (S103), and air fuel ratio difference among cylinders of the internal combustion engine at the time is suppressed (S104), and in the second place, recirculation of EGR gas using the EGR device is restarted (S105), and air fuel ratio difference among the cylinder at the time of EGR gas introduction is limited (S106), and in the third place, deterioration of the catalyst unit is diagnosed while doing recirculation of EGR gas using the EGR device (S108). <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
