Diagnostic Method 1

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Detect the malfunction by checking "Cumulative value of time when λ changes from lean → rich" in comparison to "Time during which diagnosis is in progress".

Fig 1: Front Oxygen Sensor Lean To Rich And Accumulated Time Graph

Courtesy of SUBARU OF AMERICA, INC.

Judge as NG when the following conditions are established.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria	Threshold Value	DTC
(Cumulative value of time when λ changes from lean → rich)/(Time during which diagnosis is in progress)	< 0.35	P014C
and
Average value of time necessary for λ to inverse the air fuel ratio to Lean → Rich → Lean	> 30 ms
(Cumulative value of time when λ changes from lean → rich)/(Time during which diagnosis is in progress)	> 0.65	P014D
and
Average value of time necessary for λ to inverse the air fuel ratio to Rich → Lean → Rich	> 10 ms

Time needed for diagnosis: 70000 ms

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