The auto and truck manufacturers made the disclosure in an Securities and Exchange Commission filing Friday.
"We can not predict the outcome, and we can not provide assurance that it will not have a material adverse effect on us", the automaker said in the filing.
The automaker announced the criminal investigation in its quarter earnings filing.
Ford said it is fully cooperating with the federal investigation but that it couldn't provide guidance on its outcome or how it will affect the company. The stock was up 10 percent to $10.36 as of 11:01 a.m. Friday in NY after climbing as much as 11 percent earlier. The Justice Department declined to comment. "It chooses criminal when it thinks it may find evidence that the company intentionally violated the law", said Erik Gordon, a professor at the University of Michigan's Ross School of Business.
Ford said on Friday it was fully cooperating with government agencies, as it became the latest vehicle manufacturer to be investigated over emissions.
According to Ford the DoJ probe "currently focuses on issues relating to road load estimations, including analytical modeling and coastdown testing".
Ford in the Friday regulatory filing with the U.S. Securities and Exchange Commission wrote that the "potential concern does not involve the use of defeat devices," like those used in the Volkswagen AG emissions scandal.
It's unclear whether the problems Ford discovered led to inaccurate mileage ratings.
Ford subsequently hired an outside firm to validate its own test results and then, in February, launched an internal investigation that appeared to indicate that its emissions levels were being understated, while mileage numbers were being overstated on a number of its products. The investigation and technical review will take several more months, she said.
Volkswagen paid a $4.3 billion penalty to the Justice Department in 2017 after it was caught using defeat devices to overstate the fuel efficiency of its diesel-powered models.
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