I have a 12 Boss with 9k on the engine. During some spirited driving, not near readline, flashing yellow check engine icon came on for about 10 seconds, then went off. And stayed off. I drove it home because the light stayed off, about 10 miles. Now, there is a low rpm knock in the engine. Engine runs fine otherwise, and NO lights come up. I'd considered maybe carbon buildup, though not likely, then I wondered about bad gas. Kinda afraid to drive it. At this point it's just speculation. Try some isopropyl in the fuel and add some new fuel on top of it ? Any help would be appreciated . Don.