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Whether or not you agree with the current diesel emissions limitations, the fact is that they are the law of the land. Our elected representatives have done the best they can balancing emissions, fuel mileage, and power. And the results are just the cost of doing business if you want to sell diesel vehicles in the U.S.

So keeping that in mind, it’s pretty uncool when automakers build vehicles to trick or “defeat” the emissions tests. They do it to get a bit more mpg or power out of their diesel engines. But the result is that the rest of us have to breathe more NOx gas.

Cummins Diesel-Powred Ram 3500 HD Truck towing Construction Equipment
Cummins Diesel-Powered Ram 3500 Heavy-Duty Truck Towing | Ram

One early example was when Mercedes realized that emissions testers left cars’ doors open on the dyno, so it programmed its engines to go into a sort of limp mode when the dome light was on. The famous VW “dieselgate” was a similar system that activated if the steering wheel wasn’t moving.

With automakers thumbing their noses at the EPA, its unsurprising that the Agency has been cracking down. Recently it has leveled lawsuits–such as the Ram EcoDiesel case–when it found vehicles could potentially throw off tests. Even if it never proved they were designed to.

In December 2023, Cummins and the EPA revealed not only that they had been locked in a legal battle, but that Cummins had agreed to settle outside of court. So the engine builder probably didn’t think it would have won in court. What’s more, it settled to the tune of $1.67 billion. With other fees, it’s ballooned to $2 billion. That makes it the biggest civil penalty issued under the Clean Air Act, ever.

Us automotive journalists poured over the statements by both the Agency and the company. We wondered if the engine maker had truly done nothing to mislead testers–as it claimed. We also wondered what would happen to the one million trucks, identified by the EPA, that are currently on the road. Then, today, the government gave us some key information.

David M. Uhlmann, Assistant Administrator of EPA’s Office of Enforcement and Compliance Assurance claims, “Cummins installed illegal defeat devices on more than 600,000 Ram pickup trucks, which exposed overburdened communities across America to harmful air pollution.” Knowingly? He added that Cummins “would not be paying $2 billion today if it did nothing wrong.”

This may seem sensible. But let’s return to the EcoDiesel case: the EPA had only to prove that if two separate variable co-occurred, Ram’s 3.0-liter V6 turbodiesel might mislead an emissions test. It never had to prove the automaker had done anything wrong. And you can bet your bottom dollar Cummins knows that. Is this settlement a lot bigger than the EcoDiesel? It sure is. But there are also many more affected trucks on the road.

We also learned today that as part of its settlement, Cummins has agreed to “repair” many of these trucks. Here are the specifics, it has promised to create and install a software update on at least 85% of diesel Ram HD pickup trucks from between 2013 and 2019.

If this software update just closes a possible loophole and these “repaired” trucks perform the same as they always have, the problem may be overblown. But if the EPA-mandated software update leads to less power or worse mpg–if this “fix” detunes your truck–Cummins was probably guilty.

Next, find out why deleted diesel truck owners ruined the aftermarket industry for all the other motorheads, or learn more about the history of diesel defeat devices in the video below: