The government agency said that FCA used engine management software that it did not disclose and that the undisclosed software resulted in increased emissions of nitrogen oxides from the vehicles.
USA environmental regulators on Thursday accused Fiat Chrysler Automobiles of using undisclosed software that allowed excess pollution in 104,000 diesel-powered Jeep SUVs and Ram trucks from the 2014 to 2016 model years.
EPA Assistant Administrator Cynthia Giles saying emissions software on those vehicles were not disclosed.
The testing - performed sometime after September 2015 - revealed that the FCA vehicles produce increased NOx emissions under conditions that would be encountered in normal operation and use. The scandal eventually led to around $20 billion worth of fines levied against the company and indictments of seven company executives.
Fiat Chrysler shares slumped on the news, tumbling more than 12 percent to $9.69 in early afternoon trading. Fiat Chrysler claims that its vehicle's software systems are legal. Volkswagen also formally pleaded guilty to charges of conspiracy to commit wire fraud and to violate the Clean Air Act, customs violations and obstruction of justice. Eventually, state officials said they will make sure Fiat Chrysler "brings the vehicles into full compliance" with the air pollution regulations. Both EPA and the California Air Resources Board (CARB) have issued notices of violation to FCA, and have initiated investigations based on the company's alleged actions.
The company has "spent months providing voluminous information in response to requests from EPA and other governmental authorities and has sought to explain its emissions control technology to EPA representatives", the carmaker said in a statement.
"Once again, a major automaker made the business decision to skirt the rules and got caught", said Mary Nichols, CARB's chairwoman.
WASHINGTON (AP) - Volkswagen is pleading guilty to three criminal charges and will pay $4.3 billion to the USA government for cheating on emissions tests and destroying evidence in an elaborate cover-up. The agency said it's still investigating whether these devices constitute illegal "defeat devices". Under the federal settlement announced this week, the auto manufacturer is paying a $2.8 billion criminal penalty and a $1.5 billion civil fine.