I use Amsoil in my truck and it's time to change it. (20K miles on this change) I added one can of Amsoil engine flush and high idled it for 3 -4 minutes and I looked down and my "check engine" light was on! (directions say to high idle for 15 - 20 minutes) I shut it off and went ahead and let the oil drain out. I usually let it drain all night so I know the crankcase and everything has had time to really drip down and clean out. Why did the engine flush make that light come on? Any ideas? I hope it's off tomorrow when I refill it with new oil... . Thanks for your time! JH