Table of Contents

What Changed on the L5P by Model Year

The L5P has been in HD pickups since 2017, and it runs in three phases.

Model year ECM Transmission Factory rating
2017 to 2019 E41 Allison 1000 six-speed 445 hp, 910 lb-ft
2020 to 2023 E41 Allison 10L1000 ten-speed 445 hp, 910 lb-ft
2024 and newer E42 (Global B architecture) Allison 10L1000 ten-speed 470 hp, 975 lb-ft

Two things moved at once in 2020 and again in 2024, and both affect what you can buy.

  • The transmission changed in 2020. Trucks from 2017 to 2019 use the six-speed Allison 1000. From 2020 on, the L5P is paired with the ten-speed Allison 10L1000.
  • The engine and the ECM changed in 2024. GM raised output to 470 hp and 975 lb-ft, and the hardware changed to support it. The 2024 trucks also moved to a new-generation ECM, which is the part that most often decides whether a build is possible at all.

EngineGo lists L5P parts by year range. Check the listing title and the Vehicle Fit Guide on the product page against your exact model year before checkout.

Why the L5P Is More Involved Than Earlier Duramaxes

The L5P runs the same categories of equipment as the LML before it: EGR, DPF, and DEF with SCR. What changed is how closely the ECM watches them.

  • The ECM ships locked. GM upgraded the security on the L5P, so the calibration cannot be written until the module is unlocked. How that unlock is done depends on the model year.
  • The systems are monitored together. The ECM reads NOx sensors, a DEF quality sensor, and the DPF pressure and temperature sensors, and it can reduce engine output when one of them reports a problem.
  • The transmission is a separate module. On 2020 and newer trucks, the transmission has its own control module with its own unlock.
  • The warranty check is calibration-based. GM service bulletins direct dealers to verify the calibration before authorizing powertrain warranty work, and the check is based on a checksum rather than on part numbers.

That is why hardware alone does not work on this platform. A kit without a matching calibration leaves the truck with fault codes and reduced power.

The ECM Unlock: E41 and E42

The 2017 to 2023 trucks run the E41 ECM. The unlock is done in the vehicle, but it is not a plug-in handheld job. It requires a supported interface, a dedicated unlock procedure, and software that writes the calibration after the module is opened.

The 2024 and newer trucks run the E42 ECM on GM's Global B electrical architecture, and the in-vehicle method does not work. The ECM has to be physically removed from the truck, sent to an authorized service for a bench unlock, and reinstalled. Only the ECM that came with your vehicle is accepted, because the module is paired to the rest of the truck.

Two things follow from that:

  • The unlock is a separate cost from the interface and from the calibration. Budget for all three.
  • Confirm your exact model year is supported before you buy anything else. The E41 and E42 paths are different products, and the tuner is the one part you cannot work around.

For a side-by-side of the two tuning platforms, see our EFILive vs HP Tuners comparison.

What a Complete L5P Setup Includes

A working L5P build covers four areas. Miss one and the truck will set codes and derate. 

  • DPF delete pipe. A mandrel-bent pipe that replaces the factory filter section of the exhaust. Look for factory-style hangers, band clamps, and the correct flange for your model year. See the L5P delete pipe range.
  • EGR delete kit. Block-off plates plus the gaskets and coolant hardware to close the EGR passages. The L5P job involves removing the EGR valve and cooler and capping the exhaust and coolant ports. See the L5P EGR delete kit buyer's guide for more.
  • DEF and SCR handling. The DEF tank sensors, the NOx sensors, and the DEF quality sensor have to be accounted for in the calibration so the ECM does not read the removed SCR as a fault. On the L5P this is handled in the tune rather than by a separate plug-in module.
  • Tuner and calibration. The interface, the ECM unlock, and the tune itself. Confirm your year is covered before you order, because E41 and E42 do not use the same path.

One item that is not part of a delete kit: the crankcase ventilation system. Soot from the EGR and oil vapor from the crankcase end up in the same intake tract and build into a heavy deposit there. A CCV reroute kit addresses that side, and it is a separate purchase.

A delete does not repair a worn engine, a bad sensor, or an oil dilution problem that already exists. We do not publish horsepower or fuel economy numbers for a delete, because results depend on the truck, the tune, and its condition.

Transmission and Driveline Limits

Adding power puts load on parts GM did not size for it, and on the L5P the transmission is where it shows up first.

GM rates the L5P at 445 hp and 910 lb-ft through 2023, and 470 hp and 975 lb-ft from 2024. The Allison 10L1000 in the 2020 and newer trucks is matched to that rating from the factory. Once a tune pushes torque above the factory figure, the transmission and torque converter are operating outside the range GM validated for them.

There is a second issue specific to the ten-speed. The 10L1000 is controlled by its own module, and that module is a separate unlock from the engine ECM. An engine tune that raises the torque curve without a matching transmission calibration leaves that module working from the wrong torque values, which shows up as harsh or delayed shifts. Budget for the transmission side as its own line item.

This does not mean a tuned L5P cannot be reliable. It means the driveline has to be part of the plan. Talk to a transmission shop about your truck, your tune level, and what you tow before you commit.

What GM Checks at the Dealership

If your truck is still under powertrain warranty, understand what the dealer sees.

GM service bulletins covering Duramax trucks direct the technician to read the ECM calibration before engine, transmission, or driveline work is authorized under warranty. The tool pulls two values: the calibration identification and the Calibration Verification Number, or CVN. The CVN is a checksum calculated from the calibration data actually stored in the module. Part numbers can match while the CVN does not, so the CVN is what tells the technician whether the file is a GM calibration or something else.

When a non-GM calibration is confirmed, GM's policy allows the remaining powertrain and driveline warranty to be blocked in its warranty system. GM states that this applies even if the aftermarket calibration is later removed, because coverage is based on the calibration released with the vehicle. Flashing the stock file back does not clear it.

On a truck where a set of injectors or a turbocharger runs into real money, that is the risk to weigh before you order, not after.

Fitment: What Fits and What to Check

Important: Not compatible with Cab & Chassis commercial-style trucks. Standard 2500HD and 3500HD pickup parts do not fit the 4500, 5500, or 6500 chassis cab trucks. Those trucks use different exhaust routing.

Confirm these before you buy:

  • Exact model year. 2017 to 2019, 2020 to 2023, and 2024 and newer do not share a tuning path.
  • ECM generation. E41 on 2017 to 2023, E42 on 2024 and newer.
  • Cab and bed configuration. Tailpipe exit and hanger position vary by cab style and bed length.
  • Pipe options. Check diameter and whether the listing includes a muffler.
  • What is included. Check clamps, gaskets, and coolant hardware, then list what you still need.

Both the 2500HD and 3500HD use the L5P, so the engine code is not enough on its own. For how parts differ across engines, see the Duramax delete parts interchange guide. Each product page has a Vehicle Fit Guide. Review it before checkout.

Installation Notes and Safety

Check the installation difficulty listed on each product page. The exhaust and EGR work is within reach for a confident DIY installer. The ECM unlock is not, on any year. Plan on a professional for that step.

  • Use a lift or rated jack stands. Never work under a truck held up only by a jack.
  • Let the exhaust cool completely before you start. The DPF section holds heat for a long time.
  • Soak the exhaust hardware with penetrating oil ahead of time. Rusted fasteners are common.
  • Drain and capture coolant before you open the EGR cooler. Coolant in the intake or the cylinders is a serious problem.
  • Wear safety glasses and heat-resistant gloves.
  • The unlock sequence needs a stable battery at full charge. An interrupted write can leave the module inoperable, which is a much larger repair than the job you started.

The Legal Status of an L5P Delete

This decides whether a build is an option for your truck at all.

Federal. Section 203(a)(3) of the Clean Air Act prohibits removing, disabling, or defeating any emissions control device on a certified motor vehicle, and it applies to the hardware and to the calibration that suppresses the monitors. An "off-road use only" label does not change how a certified highway vehicle is treated. Civil penalties are assessed per vehicle or per device and are adjusted for inflation each year.

California and adopting states. CARB requires an Executive Order for any add-on part that can affect emissions on an emissions-controlled highway vehicle. A part without an EO leaves the vehicle legally tampered, which affects registration and inspection. Diesel vehicles have been part of California's Smog Check program since January 1, 2010, and the inspection includes a visual check for non-approved aftermarket parts. CARB's enforcement advisory states that a violation can occur regardless of what the seller or buyer claims about intended use, so a "race use only" label is not a defense.

Inspection programs. Many states run OBD-based inspection and maintenance programs. A deleted truck typically cannot complete its emissions readiness monitors, and a monitor that reports not ready is a rejection in most programs. Tampering-related failures also frequently fall outside the repair waiver process.

Enforcement posture. On January 21, 2026, the U.S. Department of Justice said it would no longer pursue criminal charges under the Clean Air Act for tampering with onboard diagnostic systems in motor vehicles. The law did not change, and the department said it will continue civil enforcement where appropriate.

Some emissions-related products are intended only for off-road, race, or non-public-road use where permitted. Customers are responsible for confirming compliance with federal, state, and local laws before purchase and installation.

Frequently Asked Questions

Do I need a tuner for an L5P delete?

Yes. Removing the hardware without a matching calibration sets persistent fault codes and puts the truck into derate. The tune is not optional on this platform.

Why is the 2024 L5P harder to set up than earlier trucks?

The 2024 and newer trucks use the E42 ECM on GM's Global B architecture. The in-vehicle unlock used on the E41 does not work, so the module has to be removed and sent for a bench unlock before any calibration can be written. Only the original module from your truck is accepted.

Can I delete just the EGR and keep the DPF?

The EGR hardware can be installed on its own, but the ECM still needs a calibration to account for the change. Running the hardware without matching tuning sets fault codes and can cause drivability problems. Every year of the L5P is monitored closely enough that partial builds are not simpler to get right than complete ones.

Will my GM warranty still cover the truck?

GM service bulletins direct dealers to verify the ECM calibration before authorizing powertrain warranty work, and the check is based on a checksum rather than on part numbers. When a non-GM calibration is found, GM's policy allows the remaining powertrain and driveline warranty to be blocked, and that applies even if the stock calibration is put back.

Do I need anything for the transmission?

On 2020 and newer trucks, yes. The ten-speed has its own control module with a separate unlock, and an engine tune without a matching transmission calibration causes shift problems. Plan for it as a separate line item.

Does an L5P kit fit both the 2500HD and the 3500HD?

The L5P was offered in both, but the parts are not universal across everything. Confirm the model year, cab and bed configuration, and whether the truck is a pickup or a chassis cab before ordering.

How fast will an order ship?

Most orders are processed the same or next business day, excluding Sundays, unless otherwise stated. Most packages are delivered within 3 to 5 business days after leaving the warehouse, depending on package size, location, and carrier conditions. Free shipping applies to orders shipped within the continental United States.

What if I order the wrong part?

EngineGo accepts authorized returns within 45 calendar days from the date the product is received, unless otherwise specified. Returned items must be unused, uninstalled, unmodified, and in original condition with all included components. Tuner products and bundles that include a tuner may have stricter return limitations. An ECM unlock service cannot be returned once it has been performed.

Build the Right L5P Setup

Not sure which configuration fits your truck? Send us your year, model, cab and bed style, whether it is a pickup or a chassis cab, transmission, current exhaust setup, any prior modifications, and how you use the truck. EngineGo support will help you confirm fitment before you order.