The Dearborn, Michigan-based automaker said it didn't know whether it would have to correct data provided to regulators or consumers.
Kim Pittel, group vice president, said in a statement that Ford hired an outside firm to conduct an investigation into the vehicle road-load specifications used in its testing and applications to certify emissions and fuel economy.
In addition, Ford retained independent industry technical experts as part of the investigation team and hired an independent lab to conduct further coastdown testing. The company said it also was evaluating potential changes to its road-load modeling process, including engineering, technical and governance components. Ford said this week it shared its concerns with Environmental Protection Agency and California Air Resources Board officials.
The investigation and potential concerns don't involve the use of so-called defeat devices - hardware and software designed deliberately to deceive government emissions tests. At this time, Ford said there's been no determination that this affects Ford's fuel economy labels or emissions certifications.
"We plan to work with regulators and the independent lab to complete a technical review," Pittel said. "As part of our review, we have identified potential concerns with how we calculate road load. The first vehicle we are evaluating is the 2019 Ranger; we are assessing additional vehicles as well."
The EPA said in a statement on Thursday that information from Ford's investigation is "too incomplete for EPA to reach any conclusions. We take the potential issues seriously and are following up with the company to fully understand the circumstances behind this disclosure."
Shares of Ford closed down 2.57% Thursday to $8.71.