US safety regulators have opened a defect investigation into 384,608 General Motors' full-sized pickups and SUVs from the 1999-2003 model years, the safety agency said on Monday, according to Reuters. The "preliminary evaluation" by the National Highway Traffic Safety Administration, or NHTSA, covers the Chevrolet Silverado and GMC Sierra pickup, and the Chevrolet Tahoe, Chevrolet Suburban and GMC Yukon SUVs, Reuters said, citing the NHTSA. The agency has received two complaints of cracked steel wheels, the report noted.