You need to contact the US border agency to request documents for exporting your car... then you have a 72 hour hold on your car where it must be left in the us.
I have a car financed in the US (where i still work) and live in BC. the border guards told me that since I have completed the Form1 to obtain the RIV inspection sticker, that I " MUST " (his words) export it so they can ensure i have proper ICBC insurance. He said it deals with taking it out of the US economy into Canada's. And if it is registered in Canada, who ever the insurance company for your province is will require immediate coverage.
HOWEVER, I say "his words" because I've heard 1,000 conflicting stories from every border agent I have sought assistance from. This is why I'm currently trying to find every way out of exporting my vehicle since it's use for work in the states and still financed/insured as such.