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Home >> Subaru >> 2021 >> WRX STI >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (Diagnostics) (2.5L) (2 Of 4) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P0420: Catalyst System Efficiency Below Threshold Bank 1 >> Execution Condition
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Execution Condition

Secondary parameters Execution condition
Battery voltage ≥ 10.9 V
Barometric pressure ≥ 75.06 kPa (563 mmHg, 22.2 inHg)
Amount of intake air < 8.5g/s (0.3oz/s)
Accelerator pedal position = While idling
Rear oxygen output voltage after fuel cut ≤0.15V
Estimated catalyst temperature ≥480°C (896°F)
Estimated temperature of the rear oxygen sensor element ≥500°C (932°F)
(*Fuel shut-off function from the integrated intake air amount during fuel cut) > 28g (0.99oz)
Fuel shut-off function from above Not in operation

* Five seconds or more of fuel cut.