In a statement, the automaker said it discovered "nonconformities" in its final inspection process back in September 2017.
Nissan has said it has found evidence of misconduct relating to exhaust emissions and fuel economy measurements for 19 models sold in Japan. This led to the "creation of inspection reports based on altered measurement on altered measurement values", according to Nissan.
Nissan understands and regrets the concern and inconvenience caused to stakeholders as a result of its kanken issues past year.
Nissan admitted on Monday, July 9, that data on exhaust emissions and fuel economy had been deliberately "altered", dealing a blow to the Japanese vehicle giant's efforts to recover trust after an inspection scandal a year ago.
The misconduct was discovered through "proactive initiatives to prevent recurrence of such issues", although the company wouldn't explain why these initiatives were launched when they were.
The firm vowed a "full and comprehensive investigation" into its latest fake data scandal.
"A full and comprehensive investigation of the facts ... including the causes and background of the misconduct, is under way", Nissan said.
Nissan has yet to confirm which vehicles have been affected by the falsification practices, and the extent to which their fuel economy and emissions figures were altered.
This issue came to light during the course of voluntary checks conducted by Nissan.
"Nissan understands and regrets the concern and inconvenience caused to stakeholders as a result of its kanken issues a year ago".
"The Nissan vehicle-type approval average measurement values guarantee the catalog specifications for exhaust emissions", the company said. Nissan is committed to promoting and enforcing compliance and awareness thereof in all operational areas.