Mitsubishi had been in talks with Renault to get a sedan to replace the Lancer or succeed the discontinued Galant. But those discussions fell apart.
It then approached Nissan, but to no avail. In the end, Mitsubishi decided it would do without a midsize sedan, saying it will quit the segment.
But corporate tie-ups are key to helping relatively small Mitsubishi flesh out its lineup and achieve bigger manufacturing scale.
In Mexico, for instance, Mitsubishi supplies Fiat Chrysler Automobiles a rebadged version of its Attrage subcompact to sell as the Dodge Attitude.
Mitsubishi also has been in talks with FCA about supplying the Fiat brand with a version of its Triton pickup, made in Thailand.
If Mitsubishi's test fudging spills over to more vehicles, it could make other partners wary of collateral damage to their own brands, according to Nakanishi. "It is a mess," he said.
According to a report in Japan's Sankei newspaper, Mitsubishi used the wrong testing methods on its i-MiEV electric car that is sold in the United States and possibly on two other models that are sold in the U.S. market -- the Outlander Sport compact crossover and Outlander midsize crossover.
On Wednesday, April 20, Mitsubishi President Tetsuro Aikawa called a snap press conference here to admit that his company had rigged fuel economy tests on some 625,000 minivehicles sold in Japan.
They cover 157,000 units of the eK Wagon and eK Space and 468,000 units of Nissan's Dayz and Dayz Roox.
Mitsubishi said it is checking whether it mishandled tests for other nameplates sold inside Japan or in other markets. It did not say how long the investigation would take.
Mitsubishi also says it is discussing with Nissan how to compensate customers for the faked fuel economy numbers.
Mitsubishi's engineers used a running-resistance value for fuel economy tests that gave better results than the cars should get. The running resistance value is a measure of the rolling resistance of tires and air resistance when a car is moving.