The L5P Duramax engine, introduced in 2017, has powered Chevrolet Silverado HD and GMC Sierra HD trucks through today. It represents the strongest Duramax platform to date, delivering serious power, performance, and reliability.
But owners (and potential owners) often ask:
- What’s different across the L5P model years?
- What are the common problems?
- And what upgrades are most popular?
Let’s break it down.
L5P Duramax Production Years
- 2017: First year of the L5P, replacing the LML. Introduced 445 HP / 910 lb-ft torque. Known for strong reliability and a major step forward in power.
- 2018–2019: Incremental updates, better tuning support began appearing, stronger aftermarket response with intakes, exhausts, and fuel upgrades.
- 2020: Updated styling in Silverado/Sierra HD platforms, interior redesign, and 10-speed Allison transmission paired with the L5P.
- 2021–2023: Refinements in electronics, emission systems, and factory towing features. Factory power rating remained similar, but trucks benefited from more refined transmission calibration.
- 2024–Present: L5P continues as GM’s flagship diesel, with stronger emissions systems, more driver aids, and some tuning challenges due to advanced ECM encryption.
What Owners Say About the L5P
Owners generally praise the L5P for:
- Outstanding towing ability compared to older Duramax generations.
- Durability: Heavier block and internals designed for higher cylinder pressures.
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Driveability: Smooth power curve, especially paired with the 10-speed transmission* in later years.
- *Many owners prefer the 6-speed offered from 2017-2019, as the 10-speed has been reported to be problematic.
Some note downsides such as higher purchase costs, limited early tuning options, and complexity of emissions systems.
Common Problems with the L5P
- Fuel system concerns: Like all modern diesels, injector or HP4 pump issues can appear—clean fuel and quality filtration are critical.
- Emissions system components: DPFs, DEF systems, and sensors can require service or replacement, particularly for heavy-use owners.
- Electronics/ECM encryption: More secure ECMs make tuning difficult, limiting custom solutions (especially on newer trucks).
Overall, the L5P is considered by many to be a stronger and more reliable than earlier platforms like the LML or LBZ—with fewer catastrophic failures reported.
Most Popular L5P Duramax Modifications
- Cold Air Intakes: Improve airflow and help lower EGTs under heavy towing.
- Aftermarket Exhaust Systems: Better sound and reduced backpressure (emissions-compliant options available).
- Fuel Filtration & Lift Pumps: FASS Fuel Systems are extremely popular to protect injectors and pumps from air/vapor and contaminants.
- Suspension & Leveling Kits: Many owners install lift or leveling kits to fit larger tires and improve stance.
- Tuning (when available): Earlier model L5Ps have more tuning support; newer years remain limited due to encryption but aftermarket support grows over time.
L5P Duramax – A Strong Platform with Room to Grow
From 2017 through the latest models, the L5P Duramax has set the bar for GM diesel trucks. Owners value the combination of torque, towing, and reliability. While tuning newer trucks is limited for now, supporting modifications—especially in filtration, suspension, and intake/exhaust systems—continue to be top priorities.
How FASS Motorsports Can Help
At FASS Motorsports in Washington, Missouri, we stock and install the most popular L5P Duramax accessories—from FASS Fuel Systems and suspension kits to wheels, tires, and lighting.
If you’re in Franklin County or the greater St. Louis area, our expert team can help you choose and install the right upgrades for your truck.
👉 Shop L5P Duramax parts online
👉 Visit our showroom in Washington, MO for installation and local pickup
Questions? We’re Here to Help.
- Phone: (636) 429-7020
- Email: info@fassmotorsports.com