| 摘要 |
There is provided an apparatus for determining a failure of an oxygen concentration sensor, which is capable of determining a failure of the oxygen concentration sensor accurately and promptly. The oxygen concentration sensor 25 is arranged at a location downstream of a catalyst 8 in an exhaust system of an internal combustion engine 3. The apparatus 1 measures a time period elapsed after termination of a fuel cut-off operation, and calculates an integrated amount SUMSVS of exhaust gases exhausted after the termination of the fuel cut-off operation (step S13). A failure of the oxygen concentration sensor is determined depending on whether or not a signal value SVO2 of a signal from the oxygen concentration sensor 25 has crossed a predetermined threshold value #SVO2CHK (steps S51, 55). Further, when a predetermined time period #TMFCCKD has elapsed, if the signal value SVO2 has not crossed the predetermined threshold value #SVO2CHK, and at the same time when the integrated amount SUMSVS of the exhaust gases has not reached a predetermined value #SUMSVAFC (the answer to the question of the step S51 is negative (No), and at the same time the answer to the question of the step S55 is negative (No)), the failure determination is suspended (the answer to the question of the step S55 is negative (No)).
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