Cummins will recall roughly 500,000 medium and heavy-duty trucks in the Untied States due to a faulty emissions control system that it manufactured.

In a statement, the U.S. Environmental Protection Agency confirmed the recall, stating that the vehicles affected were built between 2010 and 2015. This is also the largest ever voluntary recall of trucks due to an emissions issue.

The component at fault forms part of the emissions control systems that results in excess nitrogen oxides emissions. The California Air Resources Board (CARB) discovered the defective part during emissions standards compliance tests. Tests also revealed the catalytic reduction systems to be less durable than required.

According to a Cummins spokesman, the recall will be rolled out in two phases, starting with heavy-duty trucks in August and medium-duty trucks from March 2019.

A separate recall of 232,000 Dodge 2500 and 3500 pickup trucks with Cummins engines is also currently underway.

The EPA hasn’t specified exactly which medium and heavy-duty trucks are being recalled across the United States.

Cummins has been in the spotlight for all the wrong reasons throughout the past 18 months. Not only did the company have to issue the aforementioned recall for the Ram 2500 and 3500, it was also hit with a lawsuit from owners of these vehicles claiming that a defect results in higher emissions, lower gas mileage and potentially expensive repairs.

Fortunately for the company, this lawsuit was dismissed earlier this year due to insufficient evidence with the judge saying the information provided failed to “raise a plausible inference of wrongdoing.”