Mitsubishi Motors closed down 15.2% in Tokyo after the carmaker admitted  it had tampered with tests on its mini cars to improve its fuel consumption rates. 

The Tokyo-based automaker said the issue centered on four mini car models, ek Wagon, ek Space, as well as Dayz and Dayz Roox.  It said it was testing fuel consumption using a model that deviated from regulatory requirements. The misconduct surfaced through an internal investigation implemented after customer Nissan Motor NSANY found through their own tests deviations in consumption rates and asked Mitsubishi Motors to review its methodology.  Mitsubishi Motors said it would now extend that review outside Japan.

The company plans to stop production and sales of the four models. The company is due to discuss compensation with Nissan Motors, which has also stopped sales of the models concerned, the Dayz and Dayz Roox.

Equity analysts are currently crunching numbers to determine the impact of the misconduct on earnings. The company should disclose its earnings outlook for the year ending March 2017 alongside fiscal 2016 results, which are due on April 27. For the financial year just ended it currently expects sales to have advanced 3.6% year-on-year to Y2.26 trillion ($20.7 billion) but for net profit to have dropped 15.4% to Y100 billion, with global sales volume down 3%.

In September 2015, the U.S. Environmental Protection Agency determined that Volkswagen AG (VLKAY) had tampered with its engine control unit to rig emission testing data. In February 2016, attorneys filed a class-action suit in a Caifornian court against the German automaker. The company delayed its earnings announcement for the first quarter of 2016 after postponing the presentation of its annual figures.

However, Warwick Business School Professor Christian Sandler said Mitsubishi's situation won't necessarily prove as dire.

"Where Mitsubishi has an advantage is that this may not quite have the same traction as the VW scandal as we've now been exposed to the issue already. They can also learn what went well or what went wrong in how VW handled the situation and know that the best course of action is to fully co-operate and not to hide anything as that would only bring further attention that is obviously not wanted," he said.

In the early 2000s, Mitsubishi Motors recalled its vehicles after repeatedly admitting to defects in its cars and covering them up over a prolonged period. That led to plunging earnings and an eventual bailout by affiliates.