"The issue was discovered by FCA during routine in-use emissions testing and reported to the agency," the company said. "We began contacting affected customers last month to advise them of the needed repairs, which will be provided at no charge."

FCA is recalling around 863,000 U.S. vehicles and 103,000 Canadian vehicles, the company said.

The recall was announced by the EPA on Wednesday. The agency said that the company would contact owners of the vehicles when the replacement parts were ready, and that they could continue to drive their cars in the meantime.

"EPA welcomes the action by Fiat Chrysler to voluntarily recall its vehicles that do not meet U.S. emissions standards," EPA Administrator Andrew Wheeler said in the release. "We will provide assistance to consumers navigating the recall and continue to ensure that auto manufacturers abide by our nation's laws designed to protect human health and the environment."

The impacted models are:

• 2011-2016 MY Dodge Journey (JC FWD)
• 2011-2014 MY Chrysler 200 / Dodge Avenger (JS FWD)
• 2011-2012 MY Dodge Caliber (PM FWD CVT)
• 2011-2016 MY Jeep Compass / Patriot (MK FWD CVT)

Because there are so many cars impacted, the recall will occur in the following stages, the EPA said.

1. First quarter of 2019: Model Year 2011
2. Second quarter of 2019: Model Year 2012
3. Third quarter of 2019: Model Years 2013-2014
4. Fourth quarter of 2019: Model Years 2015-2016

Customers should wait to be contacted by FCA before scheduling a dealership appointment.

"EPA will continue to investigate other FCA vehicles which are potentially non-compliant and may become the subject of future recalls," the agency said.

The news comes two months after FCA agreed to an approximately $800 million settlement resulting from claims by the U.S. Justice Department and the state of California that it used software to cheat on emissions tests for diesel vehicles. A criminal investigation into the cheating is still ongoing. In a statement about the current recall, however, FCA emphasized its routine nature.

"We are advised that today's EPA announcement reflects a new policy for announcing routine emissions recalls," Fiat Chrysler said in a statement reported by CNBC. "This campaign has no safety implications. Nor are there any associated fines."