Nissan says it has found "nonconformities" in the final vehicle inspection (kanken) procedure for domestic market vehicles at all of its Japanese factories, except the Kyushu plant.
According to the company, "performance of exhaust emissions and fuel economy tests ... deviated from the prescribed testing environment", and as a result it created "inspection reports based on altered measurement values".
After "re-verification of reliable log data", Nissan says it is confident all vehicles produced, except the GT-R, conform to Japanese standards. Furthermore these cars also meet the catalog specifications for emissions and fuel economy.
Nissan discovered these breaches while "proactively carrying out comprehensive compliance checks of various parts of its operations".
This review was mandated by Japan's Ministry of Land, Infrastructure, Transport and Tourism (MLIT) after Nissan admitted in September 2017 it had used unauthorised technicians to perform its final inspection checks for domestic market vehicles.
This failure forced the company to halt production, reinspect unsold vehicles, and recall roughly three years' worth of cars sold in Japan.
The company has launched a separate investigation into the newly discovered breach of protocol, and has retained the services of the Nishimura and Asahi law firm.
Nissan says it "understands and regrets the concern and inconvenience caused to stakeholders as a result of its kanken issues last year", and that "proactive initiatives to prevent recurrence of such issues have led to the discovery of this misconduct, for which the company is regretful".