i had this problem once before and a new front control module fixed the problem. i got back from working out of town to find a dead batteries so i jumped the truck to find my marker lights on. and they wont shut off. went and spent another 220 on a fcm (this is the 4th one in the 60000 i have had they truck) and put it in. shut the hood and all was good for a minute. then they came back on. i have the atteries unhooked right now. any guesses would be appriciated.

 

Might be a headlamp switch issue.Only prob w/ checking is that the exterior lamps will come after switch disconnect-safety default.Really the inputs to the fcm should be checked w/ a scanner,but the switch is cheaper than another fcm.Wiring also could be an issue if you've had a battery acid leak

 

Do you have a remote start or aftermarket alarm system installed? Many of these are tied into the park lamp circuit. Another place to look is your trailer connector, or any other trailer/camper wiring someone may have added. It's quite common for the rear of a trailer connector to accumulate moisture and corrode until a short circuit develops inside the connector. Even a non-corroded connector can develop a loose wire that can touch another terminal and power up a circuit.