Mitsubishi has admitted falsifying data about fuel consumption per kilometre to make its vehicles appear more efficient.
The Japanese car maker said employees tampered with data for several models sold on the domestic market by adjusting tyre pressure. The affected models include Mitsubishi’s own eK Wagon and eK Space models as well as the Dayz Roox vehicles, which it produces for Nissan.
The company, however, distanced itself from the engineers responsible for the data manipulation.
"The wrongdoing was intentional. It is clear the falsification was done to make the mileage look better. But why they would resort to fraud to do this is still unclear," said Mitsubishi’s president Tetsuro Aikawa.
Despite that, he accepted personal responsibility. "I feel responsible," he said.
The data tampering, which affected 157,000 eK Wagon and eK Space light passenger cars and 468,000 Nissan Dayz Roox vehicles, was uncovered after Nissan pointed to inconsistencies in data.
Mitsubishi reacted by conducting an internal probe, which confirmed the inconsistencies and identified tyre pressure data manipulations as the main problem.
The company said it would investigate whether data was altered for vehicles sold overseas.
"In response to Nissan's request, Mitsubishi admitted that data had been intentionally manipulated in its fuel economy testing process for certification," Nissan said.
"Nissan understands and regrets the inconvenience and concern this will cause our valued customers," the company said.
The firm said that after consulting Japan's transport ministry, it told dealers to stop selling the affected vehicles. Nissan is considering ways to help owners of the cars already sold.
Mitsubishi Motors struggled for years to win back consumer trust after a scandal in the early 2000s over cover-ups of problems such as failing brakes, faulty clutches and fuel tanks prone to falling off dating back to the 1970s.