Ford has joined the list of automakers who have been or are under criminal investigation by the US Justice Department for allegedly not adhering to emissions standards. According to Reuters, the automaker is now facing potentially significant financial penalties for violating US environmental law. The Environmental Protection Agency has declined to comment.

We reported in February that Ford had begun its own internal investigation over inaccurate emissions testing following employee concerns regarding the new Ranger pickup truck. Ford also hired an outside law firm to conduct an investigation regarding those concerns. "Ford is fully cooperating with the government, and we'll keep them posted on what we're finding through our investigation and technical review," the company said.

Ford has already submitted a new emissions testing plan for the Ranger but it still needs to be approved by regulators. Other vehicles are likely to follow but we don't know which specifics ones they are at this time. Ford will still likely face harsh financial penalties for emissions violations. "When people are not playing by the rules and they are creating more pollution… we will catch them, we will hold them accountable," said EPA Administrator Andrew Wheeler.

Unlike Volkswagen, we can confirm that so-called defeat devices are not involved in this situation, but rather the method in which the automaker tests new vehicle emissions. That method, according to whistleblowers, produces inaccurate results.

Fiat Chrysler may also soon face a criminal investigation for using illegal software to produce false results on its own diesel-emissions testing. Last January, the automaker agreed to pay an $800 million settlement to resolve claims by the Department of Justice and the state of California. Daimler is also under investigation by US regulators for excess emissions in certain Mercedes diesel vehicles.

Obviously, Ford is not alone in making errors, purposely or not, in fuel economy claims. What is certain is that the US government is taking a harsh stance against violators.