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Trying to buy a Subaru Impreza 5 door hatch, 2006. Tidy car, everything seems to be running fine. Had the timing belt, clutch and headgasket replaced in November 2018. no check engine light showing up but plugged in a code reader anyway and it says P0420- catalyst system efficiency below threshold (bank 1) asking for advice need to know in an hour

Trying to buy a Subaru Impreza 5 door hatch, 2006. Tidy car, everything seems to be running fine. Had the timing belt, clutch and headgasket replaced in November 2018. no check engine light showing up but plugged in a code reader anyway and it says P0420- catalyst system efficiency below threshold (bank 1) asking for advice need to know in an hour