2020 GMC Sierra 3500 HD

Reliability tier: verified - see /disclosure/

Engine: 6.6L Duramax L5P (Duramax, 6.6L)

Denso HP4 common-rail (no CP4 - that was the 2011-2016 LML), BorgWarner VGT turbo with electronic actuator, ceramic-tip glow plugs, in-tank lift pump; Allison 10L1000 10-speed behind the diesel (context only - engine platform).

Applicable failure modes (10)

• Cooling system wear: water pump, hoses, thermostat (towing duty)
• DEF system failures: tank heater, dosing, quality (L5P)
• DPF ash loading / excessive regeneration + differential pressure sensor
• EGR carbon buildup (valve and intake deposits)
• Fuel contamination damage to the HP4/injector system (no CP4 on the L5P)
• Glow plug failures - fragile ceramic tips (R&R hazard)
• Injector wear / pigtail-connector misfires
• In-tank lift pump / low-pressure fuel delivery stalls
• NOx sensor drift/failure (SCR efficiency codes)
• VGT turbo electronic actuator failure (BorgWarner)

Applicable parts (31)

• Cooling system refill with fresh coolant (service item, all L5P)
• Duramax L5P DEF Controller (OEM)
• DEF refill - fresh API-certified fluid (service item, all L5P)
• Duramax L5P DEF Dosing Injector, pre-2021 doser (2017-2021) (OEM)
• Duramax L5P DEF Tank Assembly (OEM)
• Duramax L5P DEF Tank Harness 2020-2022 (OEM)
• 6.6L Duramax L5P DPF / SCR aftertreatment assembly - catalog gap
• DPF cleaning service (professional bake-and-blow / thermal regeneration off-truck)
• Duramax L5P DPF Differential Pressure Sensor (OEM)
• Duramax L5P EGR Cooler (OEM)
• Duramax L5P EGR Cooler Bypass Valve (OEM)
• Duramax L5P EGR Valve (OEM)
• Duramax L5P EGT Sensor Position 3 (OEM)
• Duramax L5P Fuel Filter Upgrade Kit, spin-on conversion (Fleece Performance, 2017-2024)
• Duramax L5P Fuel Contamination Repair Kit, 2017-2023 (XDP / Alliant Power)
• Duramax L5P Fuel Filter Service Kit (OEM)
• Duramax L5P Main Fuel Filter (OEM)
• Duramax L5P Fuel/Water Separator Filter (OEM)
• Duramax L5P Glow Plug (OEM)
• Duramax L5P Glow Plug Control Module (OEM)
• Duramax L5P Glow Plug Wiring Harness (OEM)
• 6.6L Duramax L5P HP4 High-Pressure Fuel Pump (GM 12731367)
• 6.6L Duramax L5P Fuel Injector (GM 12698552, supersedes 12678992/12696966)
• 6.6L Duramax L5P injector seal/connectors - catalog gap
• Duramax L5P In-Tank Transfer (Lift) Pump (OEM)
• Duramax L5P Fuel Pump Power Control Module (OEM)
• 6.6L Duramax L5P NOx Sensor, Position 2 / Downstream 2020-2023 (GM 12747870)
• 6.6L Duramax L5P Thermostat (GM 12680457)
• Duramax L5P VGT Turbo Actuator (OEM)
• Duramax L5P Turbocharger 2020-2023 (OEM)
• Duramax L5P Water Pump (OEM)

Platform recipes (3)

• DEF subsystem repair for the L5P (mode fm-l5p-def-system): the emissions DEF hardware fails ahead of the engine - heater elements short or open (the VOQ signal clusters here), tank harnesses chafe, doser injectors crystallize
• Fuel-system health for the L5P (modes fm-l5p-fuel-contamination / fm-l5p-lift-pump): the Denso HP4 does not carry the CP4's catastrophic failure pattern, but it is not contamination-proof - dirty fuel still kills the pump and injectors
• L5P VGT turbo repair (mode fm-l5p-turbo-actuator): the BorgWarner actuator is the most common failure point on the assembly - boost leaks, limp modes and vaned-nozzle position faults

Recalls that include this truck (1)

• 24V-797 (October 24, 2024) - POWER TRAIN:AUTOMATIC TRANSMISSION:CONTROL MODULE:SOFTWARE: General Motors, LLC (GM) is recalling certain 2020-2022 Chevrolet Silverado 1500, 2500, 3500, GMC Sierra 1500, 2500, 3500, 2021 Cadillac Escalade, Escalade ESV, Chevrolet Tahoe, Suburban, GMC Yukon, and Yukon XL...

Matched by the model and model year NHTSA lists for each recall - a recall often covers only part of a year's production, so read its text for the build dates and versions it names. Whether a recall is still open on your VIN is not known here; check nhtsa.gov/recalls. All recalls, investigations and bulletins for this engine: /recalls/duramax-l5p/

Reference for this truck