Diagnostic Method 2

Change STFT (A/F compensation value) by interruption, and measure the reaction time of λ value.

When A/F sensor malfunctions, the reaction time takes longer than at normal condition. In this case, judge as abnormal.

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Measure reaction time (t1, t2, t3) and reaction time (t4, t5, t6). Use the average value of the reaction time to obtain the diagnostic value.

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Judge as NG when the following conditions are established.

Time needed for diagnosis:  4500 ms

Malfunction indicator light illumination:  Illuminates when malfunction occurs in 2 continuous driving cycles.