Diagnostic Method 1

Detect the malfunction depending on the average value of time necessary for λ to inverse the air fuel ratio from "Lean → Rich → Lean" to "Rich → Lean → Rich".

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

Courtesy of SUBARU OF AMERICA, INC.

Judge as NG when the following conditions are established.

Judgment Value

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria	Threshold Value	DTC
Average value of time necessary for λ to inverse the air fuel ratio to Lean → Rich → Lean	> 100 ms	P015A
Average value of time necessary for λ to inverse the air fuel ratio to Rich → Lean → Rich	> 110 ms	P015B

Time Needed for Diagnosis: 100 times of inversion

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