Climate|Justice Department Makes It Easier to Bypass Pollution Controls on Pickups

It was one of the easiest ways to make a diesel truck faster, more powerful and more reliable: Pay a local shop to quietly gut the emissions controls with an illegal “defeat device.”

Now the federal government has largely stopped prosecuting the people who sell and install them.

The devices, which often include both hardware and software, began exploding in popularity about 20 years ago as pollution-control systems made tailpipe emissions cleaner but put more strain on engines. Some truck owners and mechanics have called defeat devices a necessity.

By 2020, the most recent numbers available, the E.P.A. estimated that the emissions controls had been removed from more than 550,000 diesel pickup trucks over the prior decade, or roughly 15 percent of all diesel trucks originally certified with those controls. The effect, the agency found, was the equivalent of adding more than nine million additional diesel pickups to American roads, spewing harmful nitrogen oxides at levels up to 300 times the legal limits.

After a headline-grabbing case in 2015 in which Volkswagen was caught secretly using defeat-device software in millions of its cars, the Justice Department began to pursue criminal charges under the Clean Air Act against shop owners who installed the devices on individual vehicles. Those prosecutions have now ended, according to a Justice Department post on X earlier this year that went little-noticed outside the trucking world.

The policy change is in keeping with the Trump administration’s sweeping rollbacks of clean-air regulations that it argues are expensive and onerous. The White House and the E.P.A. have taken aim at greenhouse gas rules and pushed to end Biden-era efforts to encourage electric vehicles instead of those burning planet-warming fossil fuels. The agency has also targeted California’s stricter auto-emissions rules and sought to delay tailpipe standards that were scheduled to take effect next year.

In the post on X, the department said that it was “exercising its enforcement discretion” to no longer pursue criminal charges. It said it was “committed to sound enforcement principles, efficient use of government resources, and avoiding over-criminalization of federal environmental law.”