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2024 GMC Sierra 3500 HD
Reliability tier: verified - see /disclosure/
Engine: 6.6L Duramax L5P Gen2 (Duramax, 6.6L)
2024 refresh (L5P Gen2): 470hp/975lb-ft calibration with refreshed supporting hardware (high-pressure fuel pump redesign reported by vendor coverage - single source, not a parts split), 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 (18)
- Cooling system refill with fresh coolant (service item, all L5P)
- DEF refill - fresh API-certified fluid (service item, all L5P)
- Duramax L5P DEF Doser Injector 2021-2024 (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 Bypass Valve (OEM)
- Duramax L5P EGR Valve (OEM)
- Duramax L5P Fuel Filter Upgrade Kit, spin-on conversion (Fleece Performance, 2017-2024)
- Duramax L5P Fuel Filter Service Kit (OEM)
- Duramax L5P Main Fuel Filter (OEM)
- Duramax L5P Fuel/Water Separator Filter (OEM)
- Duramax L5P Glow Plug Wiring Harness (OEM)
- 6.6L Duramax L5P HP4 High-Pressure Fuel Pump (GM 12731367)
- 6.6L Duramax L5P injector seal/connectors - catalog gap
- Duramax L5P In-Tank Transfer (Lift) Pump (OEM)
- 6.6L Duramax L5P Thermostat (GM 12680457)
- 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