Toyota Motor, Honda Motor and other top Japanese automakers said on Monday that internal investigations found they had mishandled vehicle testing on dozens of models over the past decade.
Toyota said it failed to gather proper data when doing pedestrian and occupant safety tests for three models, including its popular Yaris Cross sports-utility vehicle. Honda and Mazda Motor said they had identified problems related to the testing of several models, too.
The automakers, which had been told by the Japanese government to open the investigations, said the testing failures would not affect the performance or safety of their vehicles and that customers could continue to use them normally. Still, Toyota said it would temporarily halt shipments of three of the affected models it produces in Japan. Mazda said it would suspend sales of two Japan models.
The testing problems revealed Monday by Toyota, Honda and Mazda were conducted in Japan to meet the Japanese government’s certification standards. The vehicles at issue were sold in Japan.
Suzuki Motor and Yamaha Motor also said on Monday they had found inadequate testing in the past.
The disclosures from Toyota and others add to a lengthening tally of testing and certification problems Japanese automakers have faced in recent months — issues that people in the industry worry could impact consumer perceptions of the quality of Japanese cars.
In December, an internal investigation at a Toyota subsidiary, Daihatsu Motor, revealed that most of its vehicles had not undergone proper collision-safety testing. The following month, another Toyota unit suspended all of its engine shipments after an investigation revealed it had falsified figures concerning engine power.
Japan’s transport ministry responded in January by instructing 85 companies, including car and component makers, to look into any problems that could have occurred during their testing processes.
“Given that vehicle safety and performance isn’t impacted, this latest revelation isn’t hugely critical for the companies involved,” said Satoru Aoyama, a senior director at Fitch Ratings.
But, Mr. Aoyama said, “there has long been a perception of the superior manufacturing and quality of Japanese products and with these instances of fraud appearing again and again, perceptions may be beginning to change.”
In addition to the problems Toyota found involving three current models, it also discovered errors in crash tests and other tests for four models it had discontinued.
In response to the earlier revelations of data falsification and testing problems at Toyota and affiliated companies, Toyota’s chairman, Akio Toyoda, had said he would take responsibility for turning the group around.
In a briefing on Monday, Mr. Toyoda bowed and apologized to customers.
“These acts shake the very foundation of the verification system,” Mr. Toyoda said. “They should have never been committed.”
Mr. Toyoda said he was working with Toyota group companies to identify problems with internal certification processes and work structures, and had made several trips to visit their work sites himself. “We will carry out concrete improvements,” he said.
Japan’s transport ministry said it would conduct an on-site inspection at Toyota headquarters on Tuesday to follow up on the latest disclosures.