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Home >> Subaru >> 2017 >> Forester 2.0XT Touring >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 16 (Engine Control System (Diagnostics) (P000A To P015B) (H4DO)) >> 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

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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: Air Fuel Ratio Graph (Rich And Lean)
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 λ to inverse the air fuel ratio to Lean → Rich → Lean > 94ms P015A
Average value when λ is lean > 124ms
Average value of time necessary for λ to inverse the air fuel ratio to Rich → Lean → Rich > 200ms P015B
Average value when λ is rich > 300ms

Time needed for diagnosis:  70000ms

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