LEMON Manuals
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2017
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WRX STI
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Repair and Diagnosis (Single Page)
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Engine Performance
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System
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Engine Control System (Diagnostics) (P0171 To P0685) (2.5L)
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Diagnostic Procedure with Diagnostic Trouble Code (DTC)
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DTC P0420 Catalyst System Efficiency Below Threshold Bank 1
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Component Description
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Component Description
Fig 1: Rear Oxygen Sensor Output Catalyst Function Diagram
Courtesy of SUBARU OF AMERICA, INC.
Courtesy of SUBARU OF AMERICA, INC.