NHTSA is also investigating 2004-2005 model years of the Toyota Sienna minivans equipped with run-flat tires. A dozen owners have complained about the tire pressure warning system, saying the warning light did not warn of low tire pressure.

Run-flat tires, allowing motorists to drive under 55 mph for up to 100 miles without air pressure, are standard on all-wheel drive Sienna models, spokesman Sam Butto said. He said Toyota was cooperating in the investigation.