A new study published by the Environmental Protection Agency indicates that modified diesel pickup trucks are contributing to increased levels of particulate pollution in the United States.
The EPA study, which was first reported on by The New York Times, found that an estimated 550,000 diesel pickup trucks have had their factory emissions controls removed or modified in some way over the past decade using aftermarket tuning devices. As a result, these modified trucks will emit roughly 570,000 tons of excess nitrogen and 5,000 tons of particulate matter over their lifetimes, which will have an air quality impact equivalent to adding another 9 million diesel trucks to U.S. roads.
The New York Times says the EPA first began looking into the illegally modified diesel pickup trucks after the Volkswagen diesel emissions scandal came to light in 2015. An industry-wide crackdown on companies manufacturing diesel engine tuning devices would be much harder than going after a major OEM like VW, however, as the devices are manufactured by a wide variety of companies that are usually quite small or may not be located in the U.S.
It’s not just diesel trucks that are having their factory emissions control systems re-tuned. Many of these companies manufacture devices that will reflash the engine control unit on a variety of vehicles, from turbocharged hatchbacks to commercial vans and almost everything in between.
“One reason it is difficult to estimate the full extent of tampering nationwide is that the Air Enforcement Division has reason to believe this conduct occurs within most or all categories of vehicles and engines, including commercial trucks, passenger vehicles, pickup trucks, motorcycles, forestry equipment and agricultural equipment,” the study found.
While many vehicles can easily have their ECU reflashed, heavy trucks are of the most concern for the federal environment watchdog, as they have larger engines that typically emit more emissions. Modifying the ECU on a diesel truck can not only rework the way the engine operates and increase emissions, it can also disable or change settings for crucial emisisons-reducing systems like the Exhaust Gas Recirculation system (EGR) or after treatment systems.
Aftermarket ECU systems like this can increase a truck’s horsepower or torque output. They can also be used to adjust the way emissions controls like the EGR system work and reduce the time and/or cost it takes to maintain or repair them over the truck’s lifetime, making them a popular modification among diesel enthusiasts.
General Motors offers diesel engines in both the light- and heavy-duty versions of the Chevy Silverado and GMC Sierra. The Silverado HD and Sierra HD are offered with a 6.6L L5P V8 Duramax diesel engine, while the light-duty versions of the trucks are offered with a 3.0L LM2 inline-six turbodiesel.