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 distinct phases.

Model year ECM Transmission Factory rating
2017 to 2019 E41 Allison 1000 6-speed 445 hp, 910 lb-ft
2020 to 2023 E41 Allison 10L1000 10-speed 445 hp, 910 lb-ft
2024 and newer E42 (Global B architecture) Allison 10L1000 10-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 was updated in 2024. GM raised output to 470 hp and 975 lb-ft, and the hardware changed to support it: a new turbocharger, revised pistons and cylinder heads, higher-flow injectors, and a new-generation ECM.
  • The ECM changed in 2024 as well. That is the part that most often decides whether a build is even possible, and it gets its own section below.

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 you check out.

The Emissions System on the L5P

The L5P carries a full modern aftertreatment stack. Here is what each piece does, in the order exhaust passes through it.

  • DOC (Diesel Oxidation Catalyst). Handles unburned hydrocarbons and carbon monoxide, and generates the heat the DPF needs to clean itself.
  • DPF (Diesel Particulate Filter). A wall-flow ceramic honeycomb that traps soot. When it fills, the ECM runs an active regeneration: it injects fuel after the main combustion event so the fuel burns in the DOC and raises the DPF core to roughly 1,100 degrees Fahrenheit, which burns off the collected soot.
  • SCR (Selective Catalytic Reduction) with DEF. Diesel exhaust fluid is injected ahead of the SCR catalyst, where it converts nitrogen oxides into nitrogen and water. The system depends on upstream and downstream NOx sensors and a DEF quality sensor.
  • EGR (Exhaust Gas Recirculation). Routes a metered amount of exhaust back into the intake to lower peak combustion temperature and reduce NOx formation.

Why the EGR and CCV systems interact. Recirculated exhaust carries fine soot, and the crankcase ventilation system carries oil vapor into the same intake tract. The two combine into a heavy carbon and oil deposit that builds up on intake runners, the EGR valve, and the grid heater over time. This is a known mechanism in diesel intake fouling, and it is a separate problem from a restricted DPF.

If your truck is showing DPF or DEF warnings, have a diesel shop diagnose the cause before you replace parts or order a kit. A sensor fault and a plugged filter call for different work.

The ECM Unlock: Why the L5P Is Different

Removing hardware without a matching calibration leaves the truck in derate with active fault codes. On the L5P, getting that calibration onto the ECM is the step that separates this platform from every Duramax before it.

The 2017 to 2023 trucks run the E41 ECM, which ships locked. The unlock is done in the vehicle, but it is not a plug-in handheld job. On 2020 to 2023 trucks the process requires removing a specific fuse from the under-hood power distribution center, installing a dedicated jumper harness into that fuse slot, disconnecting the batteries, and running a timed unlock sequence through a professional interface. The sequence takes several minutes and has to complete without interruption.

The 2024 and newer trucks run the E42 ECM on GM's Global B electrical architecture, and the in-vehicle method does not work at all. The ECM has to be physically removed from the truck and sent to an authorized service for a bench-level unlock, then reinstalled. Only the ECM from your specific vehicle is accepted. A spare or salvage module will be refused, because the E42 is cryptographically paired to the truck's other modules. Plan for the truck to be down while the module is away.

This is also why the tuner is not the place to save money. Both EFILive and HP Tuners support the L5P, and both require the ECM to be unlocked before either can write a calibration. The unlock is a separate cost from the interface and from the calibration itself.

For a side-by-side of the two tuning platforms, see our EFILive vs HP Tuners comparison. If you are not sure whether your truck needs an unlock at all, start with does my truck need an ECM unlock.

What a Complete 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, in 4-inch or 5-inch diameter, that replaces the factory DPF, DOC, and SCR exhaust assembly. Look for factory-style hangers, band clamps, and the correct flange for your year. See the L5P delete pipe range for the year splits.
  • 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 both the exhaust and coolant ports.
  • DEF and SCR sensor handling. The DEF tank sensors, NOx sensors, and DEF quality sensor must be addressed 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, which is another reason the calibration source matters.
  • Tuner and calibration. The interface, the ECM unlock, and the tune itself. Confirm your exact model year is covered before you order, because E41 and E42 do not use the same path.

Transmission and Driveline Limits

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

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 meaningfully above the factory figure, the transmission and torque converter are operating outside the range GM validated, and that is where converter and clutch wear tends to appear first.

There is a second issue that is specific to the ten-speed. The 10L1000 is controlled by its own transmission control 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 the TCM working from the wrong torque values, which shows up as harsh or delayed shifts. Budget for the transmission side as its own line item, not as an optional add-on.

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 specific truck, tune level, and towing load before you commit.

What GM Checks at the Dealership

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

GM service bulletins covering Duramax trucks direct the technician to read the ECM calibration before any 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 actual calibration data in the module. Part numbers can match while the CVN does not, so the CVN is what tells the technician whether the calibration is a GM-issued file 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. Putting 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 start, not after. If warranty coverage matters to you, this is the deciding factor.

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 requires 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 is the part that 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. EPA enforcement treats crankcase, EGR, DPF, and SCR delete hardware together. The "off-road use only" label does not change the analysis for a vehicle that was certified for highway use. 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 makes the vehicle legally tampered and subject to registration and inspection consequences. 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. Penalties under California law run up to $37,500 per violation, and CARB's enforcement advisory states that a violation can occur no matter what the seller or buyer claims the intended use will be. 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 the 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, which means there is no waiver path to fall back on.

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.

These products are intended only for off-road, race, or non-public-road use where permitted. Check federal, state, and local laws before purchase.

Before You Order

Confirm these before you buy, because the L5P year breaks are where wrong orders happen.

  • 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. Confirm your tuner supports your year.
  • Cab and bed configuration. Tailpipe exit and hanger position depend on cab style and bed length, and dually trucks differ from single rear wheel.
  • Pickup or chassis cab. Standard 2500HD and 3500HD pickup parts are not compatible with 4500, 5500, or 6500 chassis cab trucks.
  • Transmission. The 2020 and newer trucks need the transmission side addressed separately from the engine tune.
  • Warranty status. Decide whether a warranty block is acceptable before you order, not after.

Frequently Asked Questions

Can I use an L5P delete setup on a truck I drive on public roads?

These products are intended only for off-road, race, or non-public-road use where permitted. Removing emissions equipment on a vehicle used on public roads violates the federal Clean Air Act and many state laws, and an "off-road use only" label does not change how a certified highway vehicle is treated. You are responsible for confirming legal compliance.

Do I need a tuner for an L5P delete?

Yes. Removing the hardware without a matching calibration will trigger persistent fault codes and put the truck in derate. The tune is not optional on this platform.

Why is the 2024 L5P harder to tune 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 ECM has to be physically removed and sent for a bench unlock before any calibration can be written. Only the original module from your truck is accepted.

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 verification 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 later.

Can I reverse the delete?

You can, if you keep all the factory hardware and your tuner can flash the stock calibration back. Keep the DPF, DOC, and SCR assembly, the EGR components, and the sensors. Returning to stock does not undo a warranty block that was already recorded.

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.

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

Browse the L5P Duramax delete kits for 2017 to 2024 Silverado and Sierra 2500HD and 3500HD trucks, and check the Vehicle Fit Guide on each product page before checkout.

Not sure which configuration fits your truck? Send us your year, model, cab and bed style, whether it is a pickup or 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.