I'm not a parenting expert. So, I can tell you that you can't confiscate a car given by someone else, but I can't tell you the best way to handle a teenage boy who thinks he's too good to listen to his parents. Legally, you can take away any benefit that you've given him. Do you do his laundry? You don't have to do that. Do you cook his meals? You don't have to do that, either. I mean, you can't starve him, but you can provide groceries and let him feed himself. Of course, that may involve also providing paper plates and plastic utensils, if he doesn't clean up after himself. Do you give him snack foods like chips, soda or junk food? The law doesn't require you to provide those things. Does he park in your garage? Take away the garage door opener. Are you a joint signer on his bank account? Joint signers can close accounts. (Typically, a minor needs an adult on the account with him, but some banks have other rules depending on the child's age.) Does he park in the driveway
? Park behind him (at least for long enough to have a conversation - you'd have to move if the father showed up). You can assign other consequences to his actions. What does he want that you're giving him? Are you prepared to tell him that if he won't listen to you, he has to go live with his father? Can you lock him in his bedroom, or tell him that if he does not return by a certain time, you will lock the doors and he can go to his father's?
The other option is to go back to the family court and ask the judge to order the father to confiscate the car and not allow him to drive it. Or state that he is free to drive the truck at his father's, but that the vehicle is not allowed at your home. Tell the father that you don't' want the truck there and that he is trespassing if he does not remove it from your property.
Before taking action, though, you may want to consider talking to a parenting expert or taking your son to a family counselor. Some things that may be legal could run the risk of further alienating him, which isn't what you want. You may also run the risk that he will go to his father and ask for a change in custody. There's more of a risk of that with some more drastic punishments parents devise than if you just take him to counseling with you.