| 摘要 |
PURPOSE:To correctly perform the deterioration decision of an O2 sensor, by alarming a replacement period of the O2 sensor when it is decided that a difference between a rich side peak value and a lean side peak value of an output of the O2 sensor decreases to a predetermined value or less in the predetermined operational condition. CONSTITUTION:While an engine is in operation, it is decided whether or not a difference between a rich side peak output Vr and a lean side peak output Vl is in a condition able to perform arithmetic decision in an arithmetic decision circuit 9 from a basic injection quantity (d), calculated in an arithmetic circuit 4 on the basis of an output from an engine speed sensor 1 and an air flow meter 2, and an engine speed (a). When a decision is YES, an arithmetic circuit 13 calculates the difference (Vr-Vl) by obtaining the outputs Vr, Vl in the operational condition from a signal (c) of an O2 sensor 3. And a system, comparing an output (k) as the result with a value V0 stored in a memory 14 by a comparator circuit 15, outputs, if in a relation where (Vr-Vl)<V0, an alarm signal l, operating an alarm device 16 to alarm a replacement period of the O2 sensor 3.
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