Ford's emissions certification program is currently under the scrutinizing eye of the federal government.

Ford on Friday announced as part of a US Securities and Exchange Commission filing that it's currently subject to a criminal investigation from the Department of Justice. The investigation is focused on Ford's emission certifications program, which is used to determine fuel-economy figures and emissions compliance.

At the heart of the investigation is the "road load" estimation, which during a dynamometer (dyno) test estimates the force imparted on a vehicle from tire rolling resistance, aerodynamic drag and other factors. In its SEC filing, Ford was quick to stress that this has nothing to do with defeat devices like those found in VW's diesel vehicles. Defeat devices are intentional pieces of hardware or software meant to skirt testing processes, which is a fancy way of saying "cheating the government."

Neither Ford nor the Department of Justice immediately returned requests for comment, but in its SEC filing, Ford said it is "fully cooperating with all government agencies," and that the automaker had already notified other state and federal agencies. Ford said in the same filing that it "cannot provide assurance that [the investigation and potential outcome] will not have a material adverse effect" on the company.

Ford first announced that it was looking into its own emissions certification processes in February. At that point, a statement from the automaker said that there was "no determination that this affects Ford's fuel economy labels or emissions certifications." At the time, Ford hired a third-party firm to investigate its methodologies, which it did after several employees voiced concerns about the tests late last year.

Road-load and coastdown estimation have caught automakers in a bad way before. In 2014, Hyundai and Kia paid a $100 million civil fine after bad road-load data led to incorrect fuel-economy ratings on about 1 million vehicles. Mitsubishi admitted in 2016 to administering coastdown tests incorrectly. This year, Porsche said it was looking at data for the 2016-2017 911 after it discovered potential discrepancies with individual coastdown tests.

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