Diagnostic Method

Output fluctuation accumulate method
The accumulated value of front A/F sensor output changes and the accumulated value of rear oxygen sensor output changes are determined, and the diagnostic value is calculated using the following formula.

Diagnostic value = Accumulated value of rear oxygen sensor output changes / Accumulated value of front A/F sensor output changes
For example

Fig 1: Identifying Front Oxygen (A/F) Sensor Output Waveform
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Judge NG when the malfunction criteria below are completed, and judge OK when they are not completed.
Judgment Value

Fig 2: Threshold Value Table
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1. Time Needed for Diagnosis: 45 seconds
2. Malfunction Indicator Light Illumination: 2 continuous driving cycles.