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: Lean To Rich, Rich To Lean Air Fuel Ratio Chart

Courtesy of SUBARU OF AMERICA, INC.

• Abnormality Judgment 

  Judge as NG when the following conditions are established.

  JUDGMENT VALUE CHART
  
  

  Malfunction Criteria	Threshold Value	DTC
  Average value of time necessary for λ to inverse the air fuel ratio to Lean → Rich → Lean.	> 300 ms	P015A
  Average value of time necessary for λ to inverse the air fuel ratio to Rich → Lean → Rich.	> 400 ms	P015B

  Time Needed for Diagnosis:  50 times of inversion

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

• Normality Judgment 

  Judge as OK and clear the NG if the following conditions are established.

  JUDGMENT VALUE CHART
  
  

  Malfunction Criteria	Threshold Value	DTC
  Average value of time necessary for λ to inverse the air fuel ratio to Lean → Rich → Lean.	≤ 300 ms	P015A
  Average value of time necessary for λ to inverse the air fuel ratio to Rich → Lean → Rich.	≤ 400 ms	P015B

  Time Needed for Diagnosis:  50 times of inversion