What Do You Actually Need to Delete Your L5P Duramax?

By Lars, Lead Tech at Spetuner

I’m going to be honest with you: The 2017-2023 L5P Duramax is the hardest and most expensive truck to delete. Period.

Back in the old days, you could buy an $800 tuner and be done. Not anymore. GM locked down the L5P computer (ECM) with military-grade security. If you try to use the wrong parts, your truck won't just run poorly—it won't run at all.

I get emails every day asking: "Lars, why is the kit so expensive?" or "Do I really need the transmission tuning?"

To help you spend your money wisely, I wrote this guide. I will explain exactly what parts you need, and then I will show you which specific setup fits your driving style.

Benefits of Deleting Your L5P

Why spend the money? Because a deleted L5P is one of the best trucks on the road. Once you remove the restrictive emissions system, you unlock:

• Reliability: No more "Service DEF System" countdowns or clogged DPF filters leaving you stranded.
• Fuel Economy: Owners consistently report gaining 3-5 MPG because the engine stops wasting fuel on "Regen Cycles."
• Engine Life: By stopping the EGR system, you stop feeding dirty soot back into your engine oil. Your oil stays cleaner, longer.
• Power: The stock truck is choked. A delete tune lets the engine breathe, adding 50-150 horsepower safely.

What Do I Need to Delete My L5P Duramax?

Before we look at specific builds, here is the list of parts every single L5P owner needs to know about.

1. The "E41" ECM Problem: Why You Can't Just Tune It

The heart of the L5P is the E41 Engine Control Module. Unlike previous generations, GM encrypted this unit with a "Diffie-Hellman" key exchange protocol. In plain English: Standard tuners cannot write to this computer.

The Solution: The Swap vs. The Crack

You strictly have two options. There is no third way.

• Option A: The Exchange Service (Downtime). You remove your factory ECM (located in the driver-side fender well—it’s a pain to get to), mail it to HP Tuners or a shop, they physically open it, solder a bypass, and mail it back. Your truck is dead for 1-2 weeks.
• Option B: The New Unlocked ECM (Zero Downtime). You buy a brand-new, pre-unlocked E41 ECM from us.
  Lars’ Pick: Go with Option B. Why? Because if you ever need warranty work at the dealership, you can swap your stock, locked ECM back in 20 minutes, and the dealer’s diagnostic tools won’t see a "flash counter" discrepancy.

2. Tuning Device (The Tool)

You need a device to talk to the new computer. The most common ones are HP Tuners MPVI3 or EZ Lynk.
Note: You also need "Credits" (software licenses) to use these devices. Make sure your kit includes them.

3. DPF & CAT Delete Pipe (The Exhaust)

You need to physically remove the restrictive filters under the truck. You replace them with a "Race Pipe." This is usually a 4-inch or 5-inch stainless steel pipe.

4. CAN Bus Plugs (The Loophole)

Do not forget these! On the L5P, if you unplug the sensors under the truck, the electrical circuit breaks, and the truck won't start. You need these special plugs to cap off the harness and complete the circuit.

5. EGR Delete (The Soot Stopper)

The L5P EGR cooler sits high on the passenger side of the engine. It is prone to internal cracking, which leaks coolant into the cylinders (Hydro-lock risk).

• Block-off Plates: Cheap and easy. Stops the soot. But the cooler is still physically there and can still crack/leak coolant.
• Full Removal Kit: Harder install (4-6 hours). You physically remove the cooler and reroute the coolant lines.

Lars' Verdict: If you are keeping this truck forever, do the Full Removal. It cleans up the engine bay and removes the leak risk entirely.

6. CCV Reroute (The Oil Saver)

The Crankcase Ventilation (CCV) system vents oily mist into your turbo. Over time, this coats your turbo blades in sludge. A CCV Reroute kit vents this pressure to the atmosphere, keeping your turbo clean.

7. Computer: TCM (Transmission Tuning)

The L5P engine is strong, but the transmission needs help to hold the extra power. Tuning the Transmission Control Module (TCM) increases the pressure on the gears so they don't slip.

One Size Does NOT Fit All: We Recommend for Your Needs

At Spetuner, we don't believe in generic "one-click" solutions. A rancher towing cattle needs a completely different setup than a teenager wanting to make noise. Below are the three specific "Build Recipes" we engineer for our customers. Find the one that matches your driving style.

For The "Daily Driver"

Who Is This For? You use your truck for commuting, grocery runs, and family road trips. You are tired of the "Service DEF System" errors, but you want the truck to remain refined. You do not want it to be loud, drone on the highway, or smell like raw diesel.

The Essential Parts List:

• ECM Strategy: Pre-Unlocked E41 ECM with "Stock Power" or "Eco Tune" (+30HP). Focus is on MPG, not smoke.
• Exhaust: 4-Inch Stainless Steel with Muffler. This is critical to kill the drone and turbo whistle for a quiet cabin.
• EGR Solution: Block-off Plates Only. Since you aren't pushing high boost, plates are sufficient to stop the soot. It saves you money and hours of labor compared to a full removal.
• Transmission: Stock TCM is fine. No tuning required for this power level.

Real-World Budget & Effort:

• Estimated Cost: $2,300 - $2,600
• Wrench Time: 4-6 Hours (Medium Difficulty).
• Lars' Note: "You can do this in your driveway on a Saturday. The hardest part is physically swapping the ECM located in the fender well."

For The "Heavy Hauler" (Towing & Protection)

Who Is This For? You tow a 5th wheel, horse trailer, or construction equipment. Your truck lives at 20,000+ lbs GCWR. Your primary goals are keeping EGTs (Exhaust Gas Temperatures) low and protecting your transmission from slipping.

The Essential Parts List:

• ECM Strategy: Unlocked E41 ECM with "Tow Tune" featuring Turbo Braking assistance.
• Exhaust: 4-Inch Stainless Steel with Muffler. The 4-inch diameter maintains exhaust velocity for better low-end torque to get loads moving.
• EGR Solution: Full Removal Kit. Towing creates massive heat. You must physically remove the EGR cooler to eliminate the risk of it cracking internally and leaking coolant into the engine (Hydro-lock).
• Transmission: TCM Tuning is Mandatory. You need increased hydraulic line pressure to clamp the clutch packs tighter, preventing slip under heavy load.

Real-World Budget & Effort:

• Estimated Cost: $3,200 - $3,800
• Wrench Time: 12+ Hours (Very Hard).
• Lars' Note: "Removing the EGR cooler is brutal. The bolts are buried against the firewall. Unless you are a skilled mechanic, I highly recommend paying a shop to handle this specific install."

For The "Street Enthusiast" (Sound & Speed)

Who Is This For? You want big power (550+ HP), aggressive sound, and attention. You want to beat sports cars at the traffic light and have the loudest truck at the meet.

The Essential Parts List:

• ECM Strategy: Unlocked ECM with SOTF (Switch on the Fly). Includes a rotary switch to change power levels instantly while driving.
• Exhaust: 5-Inch Stainless Straight Pipe. Reduces backpressure for high-RPM flow. Delivers that deep, hollow "Jet Fighter" scream.
• Fueling: Aftermarket Lift Pump (FASS or AirDog). Essential to support the "Race Tune" fuel demand and protect the high-pressure pump (CP4) from starvation.
• Airflow: Cold Air Intake (CAI) to match the increased exhaust flow.

Real-World Budget & Effort:

• Estimated Cost: $4,000 - $4,500+
• Wrench Time: 8-10 Hours (Hard).
• Lars' Note: "Prepare for a long weekend. Installing the lift pump requires dropping the fuel tank or lifting the bed. Also, wiring the SOTF switch requires delicate 'pinning' work on the ECM connector."

Comparison Table

Final Warning: "Limp Mode" vs. "Dead Mode"

If your truck is currently in "Speed Limited to 55MPH" due to a DEF system failure, a delete kit will fix it. The new tune flashes over the error state.

However, if your truck is "Dead" (Won't crank) because of an electrical short, a delete kit might not fix it. Fix the electrical issue first.

Conclusion

Deleting your L5P is a big investment, but it transforms the truck. Don't just buy the cheapest kit you find on eBay. If you tow, get the Heavy Hauler setup. If you just drive to work, save your money and get the Daily Driver setup.

At Spetuner, we bundle these parts so you don't have to guess. We include the credits, the plugs, and the tunes in one box.

Find All L5P Delete Kits Here >

FAQs

Q1: Will this void my warranty?

A1: Yes. Deleting the emissions system will void the warranty on your engine and transmission. However, you can keep your factory ECM and exhaust. If you reinstall them before going to the dealer, it is possible to return to stock, but it is not guaranteed.

Q2: Why is tuning for 2020+ models more expensive?

A2: The 2017-2019 trucks use a 6-speed transmission (T87A). The 2020+ trucks use a 10-speed transmission (T93). The T93 computer is much harder to unlock, making it more expensive to tune.

Q3: Do I really need CAN Bus Plugs?

A3: Yes, 100%. Without them, the truck's computer thinks the wiring harness is cut, and the truck will not start. We include them in every Spetuner kit.

Q4: Does the "Switch on the Fly" (SOTF) come standard?

A4: Usually, no. SOTF requires extra wiring and a specific tune file. It is an upgrade option. Standard tunes usually come with a single power level (like +40HP) that you flash once.

Q5: Is a Lift Pump required?

A5: Only if you run a "Race" tune (over 150 extra horsepower). For stock power or tow tunes, the factory fuel pump works fine.