Diesel Trucking Companies Plead Guilty to Conspiring to Violate Clean Air Act

The U.S. Attorney’s Office for the District of Colorado announced on April 13 that Pro Diesel Inc. and Endrizzi Diesel, LLC. pleaded guilty to conspiring with a Colorado-based diesel shop to remove or alter the monitoring component of emissions control systems on Class 8, commercial heavy-duty diesel trucks and semi-trucks, violating the Clean Air Act.

According to plea agreements, between July 2017 and May 2020, Iowa-based Pro Diesel Inc. paid a Colorado diesel shop identified as “E.D.” more than $76,000 to disable on-board diagnostic systems on 34 Class 8 trucks. And, between January 2017 and December 2020, Missouri-based Endrizzi Diesel, LLC paid E.D. more than $149,000 to disable the diagnostic systems on approximately 60 class 8 trucks. Both diesel shops pleaded guilty to one count of violating Title 18, United States Code, Section 371.

On-board diagnostics systems, or OBDs, are monitoring devices required under the Clean Air Act to be installed on vehicles to monitor emissions control systems and to ensure they are functioning properly, according to the April 13 announcement. Tampering with an OBD is frequently referred to as “tuning.” According to the press release, one purpose for “tuning” an OBD is to allow the vehicles to continue to seemingly operate normally while the emissions control system is disabled. This reduces the high costs associated with maintaining or repairing components of the emissions control systems on heavy-duty diesel trucks.  

But tampered vehicles emit substantially more pollutants such as nitrogen oxides, carbon monoxide, non-methane hydrocarbons and particulate matter into the air, creating a risk to the environment and public health, according to the release. Nitrogen oxides from tailpipe emissions are a major contributor to the creation of ozone on the front range. Tests conducted by the Environmental Protection Agency have found that completely deleting a diesel pickup truck’s emissions controls can increase the truck’s tailpipe emissions of nitrogen oxide by a factor of approximately 310 times, carbon monoxide by a factor of approximately 120 times and non-methane hydrocarbons by a factor of approximately 1,100 times. The pollutant increase is even greater when the emission controls on Class 8 vehicles, such as the ones tampered with in this case, are disabled.

According to the April 13 release, through a remote connection, individuals at E.D. would run software programs to reprogram or “tune” the vehicle’s onboard diagnostic systems. These programs would tamper with, render inaccurate and disable the monitoring functions of the OBDs so they’d no longer detect malfunctions in the emissions control systems.

Pro Diesel will be sentenced by Judge Daniel Domenico on June 14. Endrizzi Diesel will be sentenced by Judge Regina Rodriguez on June 29. These cases are being prosecuted by Assistant U.S. Attorney Rebecca Weber and Special Assistant U.S. Attorney Linda Kato.

The case numbers are 22-cr-00064-RMR and 22-cr-00062-DDD.

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