| 摘要 |
PURPOSE: A monitoring method for a catalyst in a vehicle is provided to decide a defect regardless of deterioration of the catalyst through converting lean/rich reference lines after calculating minimum/maximum averages of an oxygen sensor at a rear end of the catalyst. CONSTITUTION: In case of a catalyst in a monitoring condition, an ECU(Electronic Control Unit) detects an amplitude and a frequency of an oxygen sensor at a rear end of the catalyst. In case of the amplitude and the frequency under an established value, the ECU decides normal state of the catalyst for identifying a rear end oxygen sensor reference line with the established value. After calculating lean and rich times between front and rear end oxygen sensors for calculating time rate of lean and rich times. Moreover, a catalyst deterioration exponent is calculated for one cycle of the front end oxygen sensor. The ECU accumulates the catalyst deterioration exponent and monitored number. In case of the monitoring number over an established time, the catalyst deterioration exponent is compared with an established value. In case of the catalyst deterioration exponent over the established value, an error is displayed.
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