US custom needs to hold exported vehicle for 72 hours in US. So You'll have to fax vehicle title to US custom 72 hour ahead before you landing. When you acorss the board, you need to stop US custom. Tell the officer that you faxed vehicle title 72 hours ago. They'll dig into those documents to find out copy of your title, when they verify that you in deed reported exporting 72 hours before, they'll put a stamp on the original title to claim this vehicle is exported. Now you have this title to Canada Custom, they'll let you know import the vehicle.
Besides this, when you are in US. you'll need to go to dealership to request a record of vehicle re-call history. Say, if you have 2008 Honda Accord LX, you need to ask the dealer to issue this type of vehicle re-call clearance. You'll need this doc when you register the vehicle in Canada.
Good Luck!