Cummins’ $1.6B Diesel Tampering Saga Raises More Questions Than Answers

Neither Cummins nor the feds will explain precisely how the company skirted emissions controls and earned itself a historic fine.

byCaleb Jacobs|
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You might have heard by now that Cummins has agreed to pay a colossal $1.67 billion to settle claims that it violated the Clean Air Act. The United States Department of Justice dropped the bombshell just before Christmas, saying the diesel engine manufacturer installed emissions defeat devices on nearly a million Ram pickups from 2013 to 2023. In turn, the DOJ claims these trucks polluted "thousands of tons" of excess nitrogen oxide (NOx) and now Cummins is paying the department's second-largest environmental penalty ever.

The thing is, no details of how Cummins managed to bypass emissions requirements have been disclosed, and the industry giant denies any wrongdoing.

Now, we've heard that argument before from too many corporations to count. I can't say whether or not Cummins is telling the truth, though what's for certain is the company agreed to pay the single largest civil settlement arranged by the DOJ under the Clean Air Act. But nothing has been released by the feds so far saying explicitly how Cummins tampered with emissions controls on these 960,000 diesel pickups. Attorney General Merrick B. Garland said simply in a statement, “The types of devices we allege that Cummins installed in its engines to cheat federal environmental laws have a significant and harmful impact on people’s health and safety."

The term "defeat device" has evolved into a blanket categorization including software and hardware that illegally increases vehicle emissions for the sake of performance, efficiency, or both. It's become common parlance in the automotive industry, especially as companies including Volkswagen have been caught using said devices to skirt emissions regulations on a massive scale. From there, it spread to the vehicle aftermarket and, particularly, the diesel tuning industry.

That's where Kory Willis, founder of PPEI Tuning, fits into this. I spoke with Willis for a story I wrote in 2020 about the Environmental Protection Agency's war on modified diesel trucks, which he's especially qualified to talk about. That's because the EPA hammered him and his company with $3.1 million in criminal fines as well as civil penalties for violating the Clean Air Act. He then signed a consent decree which allows PPEI to continue selling performance upgrades so long as they're approved by the California Air Resources Board, or CARB.

Kory Willis Kory Willis

Willis went on The Truck Show Podcast recently to talk about Cummins' massive settlement, and he put it plainly: "I don't think Cummins did anything wrong." He emphasized his personal experience with the 6.7-liter engine in question, saying he deals with them "20+ times a day" as PPEI provides owners with tuning adjustments and the like.

"What strikes me more than anything is, if there was a defeat device—or unless it was from day one, which I don't think is necessarily possible because I've passed CARB emissions with this stuff as well—I haven't seen any change," Willis explained. "That's where I'm very curious of what they're calling a defeat device."

The most plausible explanation is a software change within the engine's computer system, though exactly what alteration allegedly violated the Clean Air Act remains unclear. Willis mentioned this during his interview, as well as a particulate matter sensor that may have been absent or changed without approval. It's impossible to say for sure since Cummins and the DOJ have yet to disclose it officially.

Peter Treydte SEMA

While genuine insight is hard to come by in this case, there is at least one more source with relevant information to help make sense of Cummins' emissions testing debacle. That's Peter Treydte, the compliance center manager at SEMA Garage who works to help OEMs and aftermarket suppliers alike meet federal regulations. In the same episode of The Truck Show Podcast, Treydte shared some knowledge about the compliance process and what tools manufacturers use to stay within the feds' set parameters.

A crucial component is a vehicle's auxiliary emissions control device, more commonly referred to as an AECD in the manufacturing and testing realm. Both software and hardware can be classified as an AECD, and as Treydte puts it, they exist "to protect components under adverse conditions." He used the example of a device that alters the air-fuel ratio of an engine when under heavy load to prevent the catalytic converter from melting down.

"In this case, it appears that there were some AECDs that were being employed that were undisclosed to CARB and EPA," Treydte said. "So the way I interpret that is the Cummins engineers were doing their job. They were putting the effort in to ensure that the DPF and the catalysts were all protected under certain operating conditions, but in doing so, either the paperwork didn't get done or somehow or another, it wasn't disclosed to the agencies, and as a result, they're now suffering the consequences of that."

Again, this is speculation, but it's informed by Treydte's deep knowledge of the automotive emissions test cycles and regulations. It's very well possible that such a seemingly minor change would go unnoticed by tuners like Willis, especially if the AECD was a form of software that operates deep within the truck's engine control unit. These are complex systems.

Cummins has likely known this day was coming. Company officials have been vocal about their cooperation with the federal government throughout this process, and even now that the ink is dry on the settlement agreement, Cummins maintains its belief that no one acted in bad faith. That doesn't change the result, but understanding the situational context helps paint a fuller picture. Either way, the federal government has landed a real haymaker on one of the industry's biggest players.

Got a tip or question for the author? Contact them directly: caleb@thedrive.com

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