Someone asked "How could using non Harley plugs set a code"? Another person mentioned using the Champion brand spark plugs as an alternative to the Harley brand plugs. I am not a Harley engineer by any means but I have been told by a family member who does work in the York plant that the Harley brand plugs use a different resistor than the Champion plugs which will cross reference from the Harley plugs. He says that when the bikes internal computer (2008 & 2009) adjusts the spark a bit due to different gasoline octanes and conditions, it relies on these Harley plugs with their special resistor to do this correctly. He also says that if you use the Screaming Eagle add on plugs which the dealers push so hard, you will also not have benefit of the special resistor which the stock 6R12 uses. When it comes to plugs and oil filters, I always stick to what the manufacturer sells.