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Home >> Subaru >> 2019 >> WRX STI >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System (Diagnostics) (STI) (1 Of 4) >> Diagnostic Procedure With Diagnostic Trouble Code (DTC) >> DTC P015A: A/F/O2 Sensor Delayed Response - Rich To Lean Bank 1 Sensor 1 >> Diagnostic Method 1

Diagnostic Method 1

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

G08317433Courtesy of SUBARU OF AMERICA, INC.

Judge as NG when the following conditions are established.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
Average value of time necessary for A to inverse the air fuel ratio to Lean → Rich → Lean >190 ms P015A
and    
Average value when A is lean >250 ms  
Average value of time necessary for λ to inverse the air fuel ratio to Rich → Lean → Rich >70 ms P015B
and    
Average value when λ is rich >150 ms  

Time needed for diagnosis:  90 seconds

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