Hello everyone I am new to the site but did search this topic before posting a Q. My problem is this: (fyi the truck is a 2000 2500LD with the 6.0, 125K on the clock) I was towing my camping trailer (about 6000#) to the storage building today when (going up a steep grade) I the motor started to knock. It was definatly the top end of the motor...sounded like valves knocking from cheap gas. i eased up a bit and it quited down somewhat. When i got to the top the service engine light started flashing (i assume that indicates a misfire) Pulled off the road, shut the motor off and restarted...NO NOISE NO LIGHT. the next hill same thing. Got the camper to the storage lot and came home....NOT A SOUND or LIGHT the whole way home. Get home put it on my OBD2 computer NO CODES! I don't know where to start to troubleshoot a problem like this....if i can't get it to knock then i can't fix it. I don't know how much it has to do wiht the issue but this is the first i have towed (anything heavy) in such cold weather before, about 20F. Fuel related? Temp related? OR bigger problems? any advice, help or sugustions are very welcome.