Engine manufacturer Cummins will pay a $1.67 billion fine for emissions cheating with diesel engines in Ram pickup trucks.

The fine settles a case brought by the U.S. Justice Department and the State of California claiming Cummins violated the Clean Air Act by installing so-called defeat devices that allowed its diesel engines to cheat emissions tests. It’s the largest civil penalty ever secured under the Clean Air Act and the second-largest environmental penalty ever, U.S. Attorney General Merrick Garland said in a statement.

The defeat devices were allegedly installed on 630,000 engines in 2013 to 2019 Ram 2500 and 3500 pickups, according to a Justice Department press release. The settlement also covers “undisclosed auxiliary emission control devices” allegedly installed on 330,000 engines in Ram 2500 and 3500 trucks from model years 2019 to 2023.

“The types of devices we allege that Cummins installed in its engines to cheat federal environmental laws have a significant and harmful impact on people’s health and safety,” Garland said, adding that these engines emit “thousands of tons of excess emissions of nitrogen oxides.”

These are the same emissions at the root of the Volkswagen diesel scandal, in which VW was also accused of using defeat devices to allow diesel vehicles to pass emissions tests while in reality releasing excess pollutants that produced serious health effects. A 2017 MIT study estimated that the excess emissions produced by VW diesels caused 1,200 premature deaths.

In the wake of the revelation of VW’s emissions cheating, a lawsuit was filed allegedly illegally-high emissions in older Dodge Ram pickups with Cummins engines. These were from model years 2007 to 2012, before Ram was split off into a separate brand. Cummins later issued a recall, while Ram 1500 pickups with a different diesel engine were also recalled around that time.

2019 Ram 2500 Heavy Duty

In recent years Cummins has attempted some technology pivots—including potentially to hydrogen fuel-cell tech. It showed a fuel-cell semi truck prototype in 2019, and a battery-electric demonstrator prior to that.

Regulators don’t just have to worry about manufacturers violating emissions rules. Illegal emissions tampering on diesel pickups by owners is a big business that the EPA has also been cracking down on. It’s slapped a number of different aftermarket companies with fines, including a $1 million fine for diesel performance parts manufacturer Sinister Diesel announced in August. That company and others have sold parts advertised as improving performance, but that also disable emissions controls.