"Nissan understands and regrets the concern and inconvenience caused to stakeholders," the company said in a statement. The disclosure is the latest blow for Nissan, one of Japan's three biggest automakers and a symbol of the country's ability to turn out quality products at mass-market prices. In October, the automaker brought its Japanese factories to a halt and began recalling 1.2 million vehicles after it discovered that vehicle inspections had been carried out by uncertified technicians. Mitsubishi Motors and Suzuki Motor said two years ago that they had used improper methods on tests that exaggerated the fuel economy of their vehicles. Like Nissan, Subaru said in October that its employees had improperly conducted vehicle inspections. More broadly, a number of Japanese factory owners have been rocked in recent years by safety and quality issues. The airbag maker Takata has been blamed for a dozen passenger deaths, leading to the largest auto recall in history.