http://www.nhtsa.gov/cars/rules/ruli...nalrule.6.html

""Specifically, it proposed to require passenger cars, multipurpose passenger vehicles, trucks, and buses with a GVWR of 4,536 kg (10,000 pounds) or less, except those with dual wheels on an axle, to be equipped with a TPMS to alert the driver when one or more of the vehicle�s tires, up to all four of its tires, are significantly under-inflated. The NPRM was drafted so as to be technology-neutral, so as to permit compliance with any available TPMS technology that meets the performance requirements.

More info here - http://sprinter-source.com/forum/sho...highlight=tpms