Diagnostic Method 3

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.

Fig 1: Front Oxygen (A/F) Sensor Signal (Diagnostic Method 3)

Courtesy of SUBARU OF AMERICA, INC.

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.

Fig 2: Front Oxygen (A/F) Sensor Timing Graph (Diagnostic Method 2)

Courtesy of SUBARU OF AMERICA, INC.

Judge as NG when the following conditions are established.

Judgment Value 

Time Needed for Diagnosis:  1000 ms x [1 time(s)/2] + 1000 ms x 3 time(s) + 500 ms

Malfunction Indicator Light Illumination:  Illuminates when malfunction occurs in 2 continuous driving cycles.