19 Outback 3.6R 54k miles, knocking sound/ Blinking EL Codes: PO300, PO304, P219

Hi, this is Bo, an auto expert on RepairPal's Car Genius team! With those codes (P0300, P0304, and P219B) and a knocking sound on your 2019 Subaru Outback 3.6R, it sounds like the engine is misfiring—specifically in cylinder 4 (P0304). The P0300 is a general misfire code, and P219B points to a fuel/air mixture imbalance on one side of the engine. The misfire could explain the knocking sound, especially under load. Swapping the plugs and coils might help, but that sound could also suggest a fuel injector issue, or even a more serious mechanical problem like a valve or piston issue. If the knock doesn’t improve after changing the plugs and coils, get it checked out ASAP—before it becomes an even pricier repair! If you need any further advice or want help finding a trusted RepairPal shop in your area, please feel free to call us at 877-913-1554!