| 摘要 |
PROBLEM TO BE SOLVED: To provide an active state detecting method by which the active state of a full-range air-fuel ratio sensor can be detected accurately irrespective of the voltage fluctuation of the sensor after the supply of an electric current to the sensor is stopped. SOLUTION: After an engine is started, the supply of an electric current to a heater 70 is started (S00) and an electric current Icp for pumping is made to flow to an electromotive force cell 24 (S10). After the elapse of a prescribed period of time Tin is waited (S18), the voltage Vs across both electrodes of the cell 24 is detected (S20) and the voltage is adjusted to Vs0 (S22). Then the supply of the current Icp is stopped (S30) and waited (S35) for the elapse of 25ms. When 25ms has elapsed, the voltage Vs across both electrodes of the cell 24 is detected (S40) and the voltage is adjusted to Vs1 (S45) and the resistance value Rs1 of the cell 24 is calculated from the voltages Vs0 and Vs1 and current Icp (S50). After the resistance value Rs1 is calculated, the value Rs1 is compared with a preset value Rss (S55) and, when the Rs1 is smaller than Rss, it is discriminated that the cell 24 reaches an active state. |
