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Cummins ISX EGR Delete Guide: CM871, CM2250 & CM2350
November 9, 2026

Cummins ISX EGR Delete Guide: CM871, CM2250 & CM2350

The “Cummins ISX” badge has been stuck on three different engines over the last couple of decades, and they do not all take the same EGR hardware. That is the single fact that decides whether the block-off plates you order will actually line up. Order a kit for the wrong engine code and the plates either will not seat or they leave a port half-open — which means you have just traded an EGR problem for an exhaust leak or a coolant leak. This guide walks through the three engine generations you will actually run into, what separates their EGR systems, and how to confirm which kit your truck takes before you spend the money. 

The three engine codes that matter here are CM871, CM2250, and CM2350. They share the ISX name and a family resemblance, but the EGR layout changed between generations, so the sealing hardware changed with it. Read the engine code first, then the kit.

What the ISX EGR System Actually Does

Exhaust Gas Recirculation does exactly what the name says: it pulls a measured amount of exhaust gas out of the exhaust stream and feeds it back into the intake. The point is to lower peak combustion temperature, because hot combustion is what produces oxides of nitrogen (NOx) — the pollutant the EPA cares about most on these heavy-duty engines.

On the ISX, that loop runs through three main pieces. The EGR valve meters how much exhaust gas gets recirculated. The EGR cooler is a heat exchanger that sheds heat from that gas before it re-enters the cylinders, with engine coolant on one side and exhaust gas on the other. And a crossover passage connects the exhaust side to the intake side, carrying the cooled gas back around.

The tradeoff is soot. Diesel exhaust carries soot, and every bit of it that gets routed back into the intake deposits itself somewhere — on the valve, inside the cooler, across the crossover, along the intake runners. Over hundreds of thousands of miles, that soot becomes a restriction and, eventually, a failure point.

Common ISX EGR Problems

These engines work hard, and the EGR system is often the first thing that complains about it. The problems owners and fleets report most often, and where they usually point:

Symptom Most likely EGR culprit What to inspect first
Rough idle, power loss, CEL
 Sticking EGR valve from deposit buildup Valve movement & EGR flow codes
Loss of power, rising intake restriction Carbon-choked intake & crossover Intake passages & crossover for soot
Mystery coolant loss with no puddle EGR cooler cracking internally Coolant level & pressure test
Soot leaks in engine bay
 Exhaust leak at an EGR connection Gaskets and joints for soot trails
Fault codes with derate behavior EGR sensor or flow mismatch Scan codes before touching hardware

One thing worth being blunt about: these symptoms point toward the EGR system, but none of them prove it on their own. Coolant loss can come from a dozen places. A power complaint can be fuel, boost, or injectors. A block-off kit seals the system out — it does not tell you what was actually wrong. Pull the codes and confirm the diagnosis before you start buying parts.

Why the EGR Cooler Deserves Attention 

Of everything in the loop, the cooler is the part that tends to fail in the most expensive way. It lives under constant thermal load — hot exhaust gas on one side, coolant on the other — and it cycles through those temperatures every time the truck runs. That cycling stresses the core. When it cracks internally, coolant can make its way into the intake, which is the classic “mystery coolant loss” on a truck that is not leaving a puddle under it.

Watching the coolant level is the cheap early warning. A truck that is slowly using coolant with no visible leak, combined with EGR-related codes or soot in the intake, is worth checking against a cooler that is on its way out. Not every ISX cooler fails — plenty run their whole life — but when one does, it is the kind of failure that gets expensive in a hurry if it goes unnoticed.

CM871 vs. CM2250 vs. CM2350: Know Your Engine Generation

This is where the wrong kit gets ordered. The ISX carried three engine codes across roughly a decade, and those three codes do not map one-to-one onto interchangeable hardware.

CM871 (2007–2010)

The CM871 is the earlier of the three, built to the EPA 2007 emissions standard. It is an ISX platform whose EGR system uses its own valve port, crossover, and cooler mounting layout. On the fitment side, this is the engine where the ports and passages were laid out one way — and that way changed when the next generation arrived.

The practical point for ordering parts: the CM871 takes its own kit. It is also not the same as the CM870, the even earlier 2002–2007 ISX. If your truck is a 2002–2007, that is a different engine with a different EGR layout and a different kit entirely.

CM2250 (2010–2012)

The CM2250 is the first of the later ISX15 platforms, built to the EPA 2010 standard. This is where the emissions picture got more complicated — the EGR system now works alongside a diesel particulate filter (DPF) and, on many trucks, selective catalytic reduction (SCR) that uses diesel exhaust fluid. The EGR valve, cooler, and crossover moved to a new layout compared to the CM871.

CM2350 (2013–Present)

The CM2350 is the newer ISX15 control platform, built to the EPA 2013 standard. The EGR, DPF, and SCR systems work together with finer engine control and emissions monitoring than the CM2250. On the fitment side, the EGR valve and cooler mounting points stayed close enough to the CM2250 that the two later engines are commonly covered by the same sealing hardware — but treat that as a listed fitment to confirm, not a rule to assume.

The Three Generations at a Glance

Engine code Typical years Platform Emissions era Kit it takes
CM871 2007–2010 ISX EPA 2007 CM871 Stage 2 Plug Kit
CM2250 2010–2012 ISX15 EPA 2010 CM2250/CM2350 Stage 2 Kit
CM2350 2013+ ISX15 EPA 2013 CM2250/CM2350 Stage 2 Kit

Two points stand out. First, the CM871 and the CM2250/CM2350 do not share EGR hardware — the valve port, crossover, and cooler mounting changed between the EPA 2007 and EPA 2010 generations, so a CM871 plate will not seal a CM2250 head, and the reverse is true too. Second, the year range is a guideline, not a guarantee — 2010 is a transition year, and trucks land on either side of a model-year line depending on build date and spec. These year ranges are general references: verify the engine control module designation and engine serial number before selecting a kit.

What Is a Stage 2 EGR Plug Kit?

Once the EGR valve and cooler come out, you are left with open ports — exhaust passages, intake passages, and coolant connections that all have to be closed off. A block-off kit is the hardware that seals those ports, and “Stage 2” describes how much of the system it covers.

Stage 1 vs. Stage 2

Stage 1 Stage 2
Coverage
EGR valve port
Valve, crossover, cooler & coolant ports
What it leaves behind Internal cooler passages still open Ports sealed across the whole system
Leak risk Residual leaks & pressure loss possible Fewer open passages, fewer leak paths
Best for A partial or basic block-off Post-EGR delete full seal

Stage 2 is not a universal industry standard or a guaranteed performance upgrade. Here, it refers to a more complete set of sealing components matched to the specific EGR port configuration of each engine generation. Compare the included plates, plugs, and gaskets rather than relying on the stage designation alone. The difference matters because an unsealed port does not just sit there. An open coolant passage drains the cooling system. An open exhaust crossover cooks the wiring and sensors sitting nearby. Sealing every port instead of one is the difference between a clean job and a leak you chase later.

The Two Seguler Stage 2 Kits

Both of the kits below are Stage 2 sealing hardware for the Cummins ISX, but they are built for different engine generations and do not swap between them. Here is what each one covers.

CM871 Stage 2 EGR Plug Kit (2007–2010)

For the 2007–2010 ISX CM871, this is a Stage 2 plug kit that seals the EGR system after the valve and cooler are removed.

What it seals. The kit includes four plates, plug fittings, and gaskets that close off the EGR valve port, the exhaust crossover, and both coolant circuit connections. That is the full set of passages left open once the factory EGR hardware comes out — closing all of them is what keeps exhaust gas and coolant from finding a way out.

For 2007-2010 Cummins ISX CM871 EGR Plug Kit Stage 2 Plates and Plugs AluminumHow it is built. The plates and hardware are CNC-machined aluminum with 304 stainless steel plates and fasteners, sized for the heat and thermal cycling a working heavy-duty engine sees. 

Fitment. This kit is for the CM871 only. It does not fit the earlier CM870 (2002–2007), which uses a different EGR layout and takes its own separate kit — and it does not fit the later CM2250/CM2350 engines.

CM2250 / CM2350 Stage 2 EGR Delete Kit (2010–Present)

For the 2010-and-newer ISX15, this is a Stage 2 kit that seals the EGR system on both the CM2250 and CM2350.

What it seals. The kit uses block plates on both sides of the EGR manifold — one on the hot side where it meets the exhaust manifold, one on the cold side where it meets the intake manifold — plus high-pressure threaded plugs for the remaining passages. That closes off the EGR valve and cooler ports across the system.

For 2010-Present Stage 2 ISX 15 CM2250 CM2350 EGR Delete KitHow it is built. The sealing surfaces are anodized and CNC precision-machined for a flat, corrosion-resistant contact across the intake-side ports.

Fitment. This kit is listed for the CM2250 and CM2350. It does not fit the earlier CM871 — the sealing hardware does not swap between generations. Confirm the kit’s engine-code fitment against your own engine before ordering, rather than assuming the two later engines take identical plates sight unseen.

Both kits are sealing hardware only. What neither one includes is the calibration — the tuning that tells the engine computer the EGR system is gone. That is a separate step, covered below.

How to Identify Your Cummins ISX Engine Code

Go by the model year on the title and you are guessing. The engine itself is the reliable one.

Check the Engine Data Plate

The engine data plate is mounted on the engine, and it carries the information you actually need: the engine model, the engine code (CM871, CM2250, or CM2350), and the engine serial number (ESN). That code — not the truck’s model year, not the badge on the door — is what determines which EGR kit fits.

Why Truck Model Year Is Not Enough

Here is the trap: a 2010 Peterbilt can sit on either side of the CM871/CM2250 boundary depending on its build date and spec. Two trucks titled the same year can have different engine codes. The same is true in the CM2250/CM2350 range — you cannot split those two cleanly by year alone. The engine code is the only answer that does not guess.

Confirm the Kit Before Ordering

Engine code on the data plate Matching kit
CM871 CM871 Stage 2 EGR Plug Kit
CM2250 CM2250/CM2350 Stage 2 EGR Delete Kit
CM2350 CM2250/CM2350 Stage 2 EGR Delete Kit
CM870 (2002–2007) Not covered here — takes its own separate kit

If the plate says CM870, stop and find the CM870-specific kit. This guide covers CM871 and CM2250/CM2350, not the earlier engine.

Before You Order: A Fitment Checklist

This is the part that saves a return and a week of downtime. Run through it before you click buy:

  • Confirm the engine code. CM871, CM2250, or CM2350 — read it off the data plate, not the model year.
  • Check the EGR valve and cooler state. If the cooler is already leaking or the valve is seized, know what you are sealing off and whether other work is needed alongside it.
  • Match the ports. Confirm the kit’s plates, plugs, and gaskets cover the ports on your engine — the CM871 layout and the CM2250/CM2350 layout are not the same.
  • Check the cooling system. If coolant has been disappearing, chase that before or during the job — sealing the EGR cooler out does not fix an unrelated cooling-system problem.
  • Consider where the truck runs. Emissions rules vary by application and jurisdiction, and what is fine off-road is not fine on the highway.
  • Ask the supplier about anything uncertain. If a fitment question is not answered on the page, get it confirmed before ordering.

Installation, Tuning, and the Check-Engine Light

Installing one of these kits is a top-end job, not a filter change — the work opens exhaust passages, coolant lines, and manifold faces that all have to go back together sealed. Disconnect the negative battery terminals before starting, and keep loose debris out of any opening you are about to seal. Because this is a sealing job rather than a simple part swap, a port left half-sealed becomes an exhaust or coolant leak, and a skipped coolant plug can drain the system on the first hot run.

How the Two Kits Differ on the Bench

The two kits go in differently, and the difference mirrors the two engine generations.

The CM871 kit is a multi-point sealing job. The engine’s EGR valve, cooler, and crossover sit in a layout that, once the factory hardware is out, leaves several separate openings to close — the valve port, the crossover, and the coolant circuit connections on both ends. That is why it comes as a four-plate, multi-plug kit rather than a simpler two-plate one, and why the job needs working room around the intake and turbo side of the engine.

The CM2250/CM2350 kit is a two-plate block-off. One plate seats where the EGR manifold meets the exhaust manifold — the hot side — and the second where it meets the intake manifold, the cold side, with threaded plugs for the remaining passages. The sealing layout is simpler, but the two plates have to match the later engine’s port spacing.

Why Both Sides Get Sealed

The reason the later kit blocks both sides comes down to geometry. Blocking the cold (intake) side keeps the intake manifold’s air volume and shape from being disturbed by the now-idle EGR tubing, and removes any path that could pull unmetered air. Blocking the hot (exhaust) side returns the exhaust manifold geometry to factory spec. Sealing both sides is what keeps the job clean instead of half-done.

Understanding ECM Calibration and Emissions Monitoring

The Cummins ISX engine management system monitors EGR operation alongside the other emissions-related components. Changes to the factory emissions configuration can affect diagnostic monitoring, fault reporting, and engine operation.

Before considering any engine or emissions-system modification, understand the applicable regulations and consult a qualified diesel technician about compliant maintenance and repair options. The two Stage 2 kits here are hardware components, not complete engine management solutions.

The Aftertreatment Is Part of the Same Job

On trucks equipped with DEF, the EGR is not the only emissions system in play. Sealing off the EGR does not, on its own, resolve the DPF, DOC, and SCR side, because those systems are linked and managed together. Any change to the EGR has to be considered alongside the rest of the aftertreatment, and what is permitted depends entirely on how and where the truck is used. That leads into the next section.

Installation Considerations

A few points carry into any of these jobs. Sealing surfaces need to be clean and flat before the plates or plugs go down, and gaskets are generally not reusable — if one is disturbed, plan on fresh ones going back on. Fastener sizes and torque values vary by kit revision and engine, so follow the documentation that ships with the kit rather than a generic spec. Once the hardware is in, bring the engine to temperature and check every sealed port, the cooling system, and the fault status before the truck goes back to work.

Emissions Regulations for Heavy-Duty Trucks

EGR is one piece of a layered emissions-control system: the EGR lowers NOx during combustion, the DPF traps soot, and SCR (with DEF) handles NOx in the exhaust stream. Removing or disabling any of these on a vehicle operated on public roads is prohibited by the federal Clean Air Act.

The distinction that matters is between how a part is labeled and what the law allows. Labeling a truck or a part “off-road use only” or “competition use only” does not by itself create a legal exemption. An off-road label does not convert an on-road truck into a non-road machine. If the truck is registered and driven on public highways, the rules that apply are the on-road rules — and they do not allow disabling emissions controls.

These products are marketed for off-road and competition applications. However, product labeling alone does not establish a legal exemption — owners and operators must verify the applicable federal, state, and local requirements for their specific vehicle and intended use before purchasing or making any emissions-related modifications. This article is informational, not legal advice.

Final Thoughts

Three ideas stand out from this guide. First, the CM871, CM2250, and CM2350 are three different EGR generations, and the CM871 does not share hardware with the later pair. Second, a Stage 2 kit is a more complete seal than a Stage 1 block-off — it closes the valve port, crossover, cooler passages, and coolant connections rather than a single face. Third, and most importantly, the engine code on the data plate is the decision that comes before the kit — not the model year on the title.

Read the plate, match the code to the kit, and confirm fitment against your own engine before ordering. If the code says CM871, you need the CM871 kit. If it says CM2250 or CM2350, the later kit covers you — confirm it rather than assuming.

Find all three at seguler.com.

Frequently Asked Questions

Q: What is the difference between a Cummins ISX CM871 and CM2250?

A:The CM871 is the earlier engine, built to the EPA 2007 standard, with its own EGR valve, crossover, and cooler mounting layout. The CM2250 is a later ISX15 platform built to EPA 2010, where the EGR system works alongside a DPF and, on many trucks, SCR. The two use different EGR hardware and take different sealing kits.

Q: Is the CM2250 EGR kit compatible with the CM2350?

A:The CM2250/CM2350 kit is listed for both engines, because their EGR valve and cooler mounting points are close enough that the standard block-off hardware is commonly cross-compatible. Treat that as a listed fitment to confirm against your own engine rather than a universal rule.

Q: Are CM871 and CM2250 EGR kits interchangeable?

A:No. The CM871 uses a different EGR valve port, crossover, and cooler mounting pattern than the later engines, so the block plates and plugs do not swap between them. A CM871 plate will not seal a CM2250 head, and the reverse is true too.

Q: How do I identify my Cummins ISX engine model?

A:Read the engine data plate on the engine itself. It carries the engine code — CM871, CM2250, or CM2350 — along with the engine serial number. The door sticker and the title model year are not reliable for this, especially around transition years like 2010.

Q: What is included in a Stage 2 EGR plug kit?

A:A Stage 2 kit includes the block plates, plug fittings, and gaskets needed to seal the EGR valve port, the exhaust crossover, the cooler passages, and the coolant connections left open after the EGR hardware is removed. The exact contents vary by engine generation.

Q: What is the difference between a Stage 1 and Stage 2 EGR kit?

A:A Stage 1 kit typically covers a single surface port — usually the EGR valve mounting face. A Stage 2 kit seals the whole system: the valve port, crossover, cooler passages, and coolant connections. More ports sealed means fewer leak paths.

Q: Does the CM2350 use a different EGR system from the CM2250?

A:The two engines differ in control and emissions monitoring — the CM2350 is a newer platform — but their EGR valve and cooler mounting points are close enough that the same sealing kit is commonly listed for both. Confirm the fitment against your engine code before ordering.

Q: What should I check before ordering a Cummins ISX EGR kit?

A:Confirm the engine code off the data plate, check the EGR valve and cooler state, match the kit’s ports to your engine, check the cooling system for existing leaks, and consider where the truck is operated. Resolve any open fitment question with the supplier before ordering.

Q: Does an EGR delete require custom ECM tuning?

A:Generally, yes. When EGR flow is physically blocked, the factory calibration may no longer match the hardware change, which can set codes and trigger derate behavior. Custom ECM tuning is generally required, and the timing of that step varies by engine — follow the documentation for your truck.

A:No. Removing or disabling emissions equipment on a vehicle operated on public roads is prohibited by the federal Clean Air Act. These kits are intended for off-road, competition, and non-highway applications, and an “off-road use only” label does not by itself create a legal exemption.

Legal Disclaimer: Removing, disabling, or modifying emissions control equipment on a vehicle operated on public roads is prohibited by the federal Clean Air Act and may void your warranty under the Magnuson-Moss Warranty Act. The products discussed here are intended for off-road, competition, and non-highway use only. Labeling a vehicle or product as “off-road” or “competition use only” does not by itself create a legal exemption. Confirm federal, state, and local regulations — and your vehicle’s specific configuration — before purchasing or installing any emissions-related component. This article is provided for informational purposes and is not legal advice.

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