The Japanese automaker, which already has 6 million vehicles under recall this year, said it did not yet have a way to fix the latest problem, which affects only cars in 20 cold-weather states and the District of Columbia, the Detroit Free Press reported.
Owners in those states will be able to have their vans inspected.
The recall covers two-wheel drive Siennas from model years 1998-2010.
Toyota said rust could cause the spare-tire cable to snap, sending the tire on the road, but did not say whether crashes had been linked to the problem.
Toyota recalled 2.3 million vehicles in January due to accelerator problems that reportedly caused numerous accidents. It also has recalled millions of cars to replace or adjust floor mats it said sometimes got entangled with gas pedals. And the 2010 Prius hybrid has been recalled because of problems with its regenerative brake system software.
The Sienna recall applies to Michigan, Connecticut, Delaware, Illinois, Indiana, Kentucky, Massachusetts, Maryland, Maine, Minnesota, New Hampshire, New Jersey,
New York, Ohio, Pennsylvania, Rhode Island, Virginia, Vermont, Wisconsin, West Virginia and the District of Columbia.