By Kosaku Narioka

Toyota Motor and two other automakers suspended shipments of several models in Japan after they discovered they didn't fully follow the government's testing standards when seeking certifications on their models.

Toyota on Monday said it found it had used inadequate data for pedestrian and occupant protection tests for the Corolla Fielder, Corolla Axio and Yaris Cross as part of its investigation into the certification process.

Japan's transport ministry in January instructed domestic automakers to investigate their model certification processes after it discovered serious breaches by Toyota's small-car unit, Daihatsu Motor.

Five manufacturers, including Toyota, found that they failed to follow the government's standards for some models, the ministry said Monday. It will conduct on-site inspections at the five companies, it said.

Toyota also said there were errors in crash tests and other test methods for four discontinued models.

Toyota said there are no performance issues that violate regulations, and there is no need to stop using the cars.

"Nevertheless, these acts shake the very foundations of the certification system, and as an automobile manufacturer, we believe they are acts that must never be committed," Chairman Akio Toyoda said.

Toyota said its investigation is continuing and that it will explain to the relevant authorities and expedite appropriate measures, including conducting testing.

Mazda Motor halted the shipment of two models after finding workers had modified the engine-controlling software during power testing. The company said the vehicles are safe to drive.

Yamaha Motor stopped the shipment of a motorcycle after it discovered workers had changed the model's engine output in preparation for muffler testing.

Honda Motor and Suzuki Motor also reported inappropriate actions for some models no longer in production. The automakers said there are no performance or safety issues regarding driving these vehicles.

Write to Kosaku Narioka at

(END) Dow Jones Newswires

06-03-24 0820ET