| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a catalytic deterioration detecting device capable of precisely determining the deterioration on the basis of an accurate delay period at proper time, without depending on an operation state of an internal combustion engine, by preventing an interfering phenomenon of an air-fuel ratio waveform of a different bank. <P>SOLUTION: When a fuel cut condition is realized, the air-fuel ratio of exhaust gas from a left bank is kept in a substantially constant value on the rich side by continuing rich operation without cutting fuel in the lefty bank, and is switched to the rich operation by resuming fuel injection in response to realization of a fuel cut return condition after cutting the fuel (F/C) only in a right bank. The deterioration in an underfloor catalyst is determined on the basis of a delay period up to a rich variation in a rear O<SB>2</SB>sensor from a rich variation in a right bank front O<SB>2</SB>sensor at this time. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
