Suzuki Motor Corp., Mazda Motor Corp. and Yamaha Motor Co. have conducted improper fuel-economy inspections on more than 6,400 new vehicles since 2012, the government said Thursday, joining the list of Japanese manufacturers grilled over product data scandals.The infractions came to light after the transport ministry last month directed 23 Japanese vehicle makers to conduct in-house investigations after Nissan Motor Co. and Subaru Corp. admitted falsifying emissions or fuel efficiency data during final product testing.Suzuki, Mazda and Yamaha Motor acknowledged certain conditions such as sp…READ FULL ARTICLE