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Home >> Subaru >> 2019 >> Outback 2.5i >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System (2.5L) (Diagnostics) (2 Of 4) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P0420: Catalyst System Efficiency Below Threshold Bank 1 >> Diagnostic Method

Diagnostic Method

When TWC performance falls, OSC performance also falls. In the diagnosis, malfunction will be detected with estimation of OSC performance by observing the time and air amount, etc. until the rear oxygen sensor voltage starts to rise after more than predetermined time of deceleration fuel cut has passed.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value
Oxygen Storage Capacity (OSC) of Catalytic < 0.35g(0.01oz)

Time needed for diagnosis:  Less than 1 second

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