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Old 06-01-2020, 09:22 PM   #1
Scooby Newbie
Member#: 515250
Join Date: Jun 2020
Default P0420 catalyst system efficiency below threshold bank 1

I have a 08 Impreza wrx with a ej205 swap. I drove about 5 hours with a few brief stops to get rims. When I got back I put them on at my buddies and was on my way home I was driving the car easy and all the sudden my engine like flashed briefly then stayed on. My traction control light came on and my cruise is flashing.I ran a 3 inch straight pipe from the cat back. I have had the exhaust modified for about a month and a half 2 months befor this code popped up. Does any body have any ideas what it could befor I got takin it in to a shop.
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