DENVER — The U.S. Attorney’s Office for the District of Colorado announced Friday that Pro Diesel Inc. and Endrizzi Diesel, LLC. pleaded guilty to conspiring with a Colorado-based diesel shop to remove or modify the monitoring component of emission control systems on Class 8 commercial diesel trucks and tractor-trailers, violating the Clean Air Act.

According to the plea agreements, between July 2017 and May 2020, Iowa-based Pro Diesel Inc. paid more than $76,000 to a Colorado diesel store identified as “ED” to disable on-board diagnostic systems. (OBD) on 34 class 8 trucks.

Between January 2017 and December 2020, Missouri-based Endrizzi Diesel, LLC paid ED more than $149,000 to disable diagnostic systems on approximately 60 Class 8 trucks. Both diesel shops pleaded guilty to one count charged with violating Title 18, United States Code, Section 371.

On-board diagnostic systems are monitoring devices that, under the Clean Air Act, must be installed on vehicles to monitor emission control systems and make sure they are working properly.

Tampering with an OBD is often referred to as “tuning”.

One of the purposes of “tuning” an OBD is to allow vehicles to continue to operate normally while the emissions control system is disabled. This reduces the high costs associated with servicing or repairing emission control system components on diesel heavy-duty trucks. However, as a result, tampered vehicles release significantly more harmful pollutants such as nitrogen oxides, carbon monoxide, non-methane hydrocarbons and particulates into the air, posing a risk to the environment and public health. .

Nitrogen oxides from exhaust emissions are a major contributor to the creation of ozone on the foredeck.

EPA testing has found that completely removing emissions controls from a diesel truck can increase the truck’s nitrogen oxide emissions by a factor of approximately 310 times, carbon monoxide d a factor of about 120 times and non-methane hydrocarbons by a factor. about 1100 times. The increase in pollutants is even greater when emission controls on Class 8 vehicles, such as those tampered with here, are disabled.

Through a remote connection, ED employees ran software to reprogram or “tune” the vehicle’s on-board diagnostic systems. These programs would corrupt, inaccurate, and disable OBD monitoring functions so that they no longer detect malfunctions in emission control systems.

The accused Pro Diesel will be sentenced by Judge Daniel Domenico on June 14.

Defendant Endrizzi Diesel will be sentenced by Judge Regina Rodriguez on June 29.

These cases are being prosecuted by Assistant United States Attorney Rebecca Weber and United States Special Assistant Attorney Linda Kato.