2024 Cummins Delete: What Is On the Truck, and What Federal Law Says

This reference for a 2024 Ram Heavy Duty starts from a different question than whether a delete can be done — it starts from what is actually on the truck. It is what is on the truck, what that hardware is doing, and where the law sits. This article answers those three in order, using the truck's own owner's manual for the first two. This is written as a technical and legal reference, and it is not legal advice for your own circumstances.

The short answer

The Environmental Protection Agency names the prohibitions on tampering as Clean Air Act section 203(a)(3) and 40 C.F.R. §§ 1068.101(b).^[2] The Act prohibits anyone from tampering with an emission control device on a motor vehicle by removing it or making it inoperable, whether before or after the sale to the buyer.^[1]

Owners usually expect one of two things to change that. The first is age, and it does not. Those prohibitions apply for the entire life of the vehicle, and they apply regardless of whether the regulatory useful life or the warranty period has ended.^[3] The second is labelling, which has its own section below.

What is actually on a 2024 truck

Ram describes the Cummins diesel engine in this truck as meeting all diesel emissions standards and as one of the lowest emitting diesel engines ever produced.^[4] That result comes from two subsystems working under the engine controller rather than from the engine alone.

The first handles soot. The Powertrain Control Module manages engine combustion so that the exhaust system's catalyst traps and burns particulate matter, with no input or interaction on your part.^[4] Note what that sentence is describing: not a filter the truck merely carries, but a filter the truck actively manages by changing how the engine burns fuel.

The second handles oxides of nitrogen. The vehicle is equipped with a Selective Catalytic Reduction system to meet the diesel emissions standards required by the Environmental Protection Agency. The purpose of that system is to reduce oxides of nitrogen to a near-zero level.^[4]

This is why a delete on a truck of this generation is not a subtraction. The engine calibration, the filter and the reduction catalyst are one system, and removing part of it leaves the controller managing hardware that is no longer there.

The regeneration cycle, by the numbers

Most delete conversations start with a regeneration complaint, so it is worth setting out what the truck actually does and when.

When the diesel particulate filter is 40% full of particulate matter, the truck looks for opportunities to enter regeneration automatically, without alerting the driver or requiring any action.^[4] Nothing appears on the dash at this stage, and nothing is asked of you.

The stage that produces complaints is the next one, and its cause is a duty cycle rather than a fault. Under conditions of short-duration, low-speed driving, the engine and exhaust after-treatment system may never reach the conditions required to remove the trapped particulate matter.^[4] At 70% full the truck displays a message at key-on and in PARK telling the driver to drive at highway speeds to clear the filter.^[4] A vehicle with an analog-gauge cluster displays the words at Consistent Speed instead of at Highway Speeds. Either message will be accompanied by a single chime.^[4]

The urgency of that message is lower than its wording suggests, and the manual says so. It is not necessary to drive at highway speeds immediately to address this, or to keep driving once regeneration has started, but it should not be neglected for long.^[4] So it is a request to give the truck a longer run soon rather than an instruction to find a motorway in the next ten minutes.

There is a second message at the same loading level, and telling the two apart saves a wasted service visit. That message displays with a chime when regeneration engages automatically while the vehicle is being driven at a suitable speed. That message repeats every three minutes while the filter is self-cleaning, until the particulate level is reduced to zero.^[4] The first message is a request; the second is a progress report.

What happens if you cannot finish the drive is written down too. If time or circumstances do not allow the vehicle to keep being driven, the system resumes regeneration at its next opportunity and displays the message again.^[4] A further message indicates that the filter's self-cleaning is completed.^[4]

Leaving it longer costs time rather than parts, up to a point. The fuller the filter is, the longer the regeneration process takes to complete.^[4] If the filter reaches 90% full, a complete regeneration typically requires 45 minutes of driving to restore normal operating condition.^[4]

Past that the truck stops asking. At 100% full the truck displays Exhaust Filter Full and reduces engine power.^[4] At that point regeneration is no longer possible and the filter has to be cleaned by an authorized dealer.^[4] In extreme cases a completely full filter can damage the exhaust system, requiring part replacements.^[4]

Read as a sequence, that is a system announcing a duty-cycle problem with increasing volume. A truck that spends its life on short low-speed trips will see those messages, and the messages are accurate.

Watching the filter instead of guessing at it

Owners are often told the truck gives no warning before the expensive stage. On this generation it does, and there is a place to look. The filter gauge on the Premium Instrument Cluster remains available during regeneration.^[4] An analog instrument cluster displays the words Automatic Exhaust Regeneration In Progress in place of a value.^[4]

That single readout changes the shape of the problem. A filter climbing towards its limit on a short-trip duty cycle is visible weeks before the power-reduction message, and a long steady drive at that point costs an hour rather than a dealer visit.

Not every power reduction is the filter

This is the most common misdiagnosis behind a delete decision, because the symptom is identical and the cause is not. The truck displays messages when a derate, meaning an engine power reduction, is activated to protect the engine during start-up in cold ambient temperatures.^[4] One of those messages appears at start-up when the ambient temperature is between 10°F (-12°C) and -10°F (-23°C).^[4] The truck also has an engine warm up protection feature that may limit engine performance after cold starting at low ambient temperatures.^[4]

Read those together and the pattern is clear: a truck that feels flat for the first minutes of a cold morning is doing what the manual says it will do, and it has nothing to do with the particulate filter. A power reduction that arrives with the Exhaust Filter Full message is a different event from a power reduction that arrives at start-up below freezing.

The idle mode that raises engine speed

There is one more piece of documented behaviour that owners read as a fault. If the engine idles or the truck is driven on low engine speed drive cycles for more than two hours, the system automatically enters an emissions operating mode that raises the engine idle speed to 900 RPM.^[4] That operating mode may last for up to an hour of idle time, or around 20 minutes of driving time.^[4]

So a truck that has spent the morning idling on a job site will sit at a higher idle and feel slightly different at low speed, on purpose, to keep the filter in a condition where it can clean itself. It is the truck working around a duty cycle rather than failing at one.

The maintenance the truck asks for on its own

Separately from regeneration, the truck also asks for emissions maintenance on its own at a set interval.^[4] That maintenance may include replacing the Closed Crankcase Ventilation filter element.^[4] This is scheduled work rather than a fault, and it is worth telling apart from the filter messages above, because the two get conflated and only one of them is a symptom.

One safety point belongs with all of this, because regeneration is a heat event. A hot exhaust system can start a fire if you park over materials that can burn.^[4] Such materials might be grass or leaves coming into contact with the exhaust system.

Where the truck parks after a long drive matters more on a diesel with aftertreatment than most owners expect.

What federal law prohibits

The prohibition covers more than lifting a part off the truck, and the test EPA applies is a comparison rather than a judgement about why the work was done. When EPA decides whether service on an emissions element was tampering, it compares the element after the service against its fully functioning certified configuration.^[5]

The reference point is the configuration the truck was certified in. Software sits inside that boundary along with hardware, because a calibration written to suit absent aftertreatment is a change measured against the same reference.

Off-road and competition labels

There is no Clean Air Act exemption for a vehicle used only off-road or only for racing. A label is a description of intended use printed by a seller, and it says nothing about the certification status of the truck it ends up on.

EPA has also looked at the claim in practice. EPA has found that companies selling defeat devices claim competition-only use but cannot provide any information to show that their products are used solely in competition motorsports.^[2]

Warranty

Ram's own owner's manual states that intentional tampering with emissions control systems may void your warranty and could result in civil penalties being assessed against you.^[6] That is the manufacturer's position, printed in the book that came with the truck.

What it does not mean is that any modification automatically ends all coverage. Federal warranty law puts the burden on the warrantor to show that the aftermarket part caused the failure. Both points are worth holding at once: the manufacturer has grounds where tampering is involved, and a denial still has to connect the modification to the failure being claimed.

What the exposure is

Civil penalties under the Clean Air Act are set at 42 U.S.C. § 7524, and the current amounts are published in 40 C.F.R. § 19.4, which adjusts them for inflation. Two amounts apply to two different classes of party, and this is the distinction most often reported the wrong way round.

For any person other than a manufacturer or dealer, the maximum is $5,911 per motor vehicle or engine. For a manufacturer or dealer, the maximum is $59,114 per motor vehicle or engine.

Those amounts are maxima rather than fixed sums. The statute requires the assessor to weigh the gravity of the violation, the economic benefit gained, the size of the business and its compliance history, so the published figure is a ceiling and not a price list.

The compliant path when the filter keeps loading

If the filter keeps loading, the first move is diagnosis and duty cycle rather than hardware. The messages above distinguish a truck that is not getting the driving conditions it needs from a truck with a fault, and those two have different answers.

Where a truck has already been modified, there is a route back that EPA names. EPA generally takes no enforcement action where the person restores the element to its certified configuration.^[5]

As this reference organises it, where aftermarket parts are appropriate, the compliant categories for a road-registered truck are parts holding a California Air Resources Board Executive Order, emissions-intact tuning that does not alter an emissions control element, and restoration to factory configuration. It is worth knowing why a delete part will not appear in the first category. CARB must deny an Executive Order exemption request if the device will reduce the effectiveness of the emissions control system.

A part whose function is to reduce emissions-control effectiveness can never receive an Executive Order. That is a rule about function, not a queue. In California, Vehicle Code section 27156 separately prohibits installing, selling, offering for sale or advertising such a device.