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Duramax platform

Duramax 6.6L V8 Turbo Diesel (GM HD, L5P 2017+ generation)

2017-present · 6.6L · General Motors

40
vehicle configs
10
failure modes
34
parts
3
recipes
4 + 0
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Failure modes

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)

Parts

Cooling system refill with fresh coolant (service item, all L5P) part-l5p-coolant-service Duramax L5P DEF Controller (OEM) part-l5p-def-control-module DEF refill - fresh API-certified fluid (service item, all L5P) part-l5p-def-fluid-service Duramax L5P DEF Dosing Injector, pre-2021 doser (2017-2021) (OEM) part-l5p-def-injector-2020-2021 Duramax L5P DEF Doser Injector 2021-2024 (OEM) part-l5p-def-injector-2021-2024 Duramax L5P DEF Tank Assembly (OEM) part-l5p-def-tank-assembly Duramax L5P DEF Tank Harness 2020-2022 (OEM) part-l5p-def-tank-harness 6.6L Duramax L5P DPF / SCR aftertreatment assembly - catalog gap part-l5p-dpf-assembly-gap DPF cleaning service (professional bake-and-blow / thermal regeneration off-truck) part-l5p-dpf-cleaning-service Duramax L5P DPF Differential Pressure Sensor (OEM) part-l5p-dpf-pressure-sensor Duramax L5P EGR Cooler (OEM) part-l5p-egr-cooler Duramax L5P EGR Cooler Bypass Valve (OEM) part-l5p-egr-cooler-bypass-valve Duramax L5P EGR Valve (OEM) part-l5p-egr-valve Duramax L5P EGT Sensor Position 3 (OEM) part-l5p-egt-sensor-pos3 Duramax L5P Fuel Filter Upgrade Kit, spin-on conversion (Fleece Performance, 2017-2024) part-l5p-fleece-fuel-filter-upgrade Duramax L5P Fuel Contamination Repair Kit, 2017-2023 (XDP / Alliant Power) part-l5p-fuel-contamination-kit Duramax L5P Fuel Filter Service Kit (OEM) part-l5p-fuel-filter-kit Duramax L5P Main Fuel Filter (OEM) part-l5p-fuel-filter-main Duramax L5P Fuel/Water Separator Filter (OEM) part-l5p-fuel-filter-wif Duramax L5P Glow Plug (OEM) part-l5p-glow-plug Duramax L5P Glow Plug Control Module (OEM) part-l5p-glow-plug-control-module Duramax L5P Glow Plug Wiring Harness (OEM) part-l5p-glow-plug-harness 6.6L Duramax L5P HP4 High-Pressure Fuel Pump (GM 12731367) part-l5p-hp4-pump 6.6L Duramax L5P Fuel Injector (GM 12698552, supersedes 12678992/12696966) part-l5p-injector 6.6L Duramax L5P injector seal/connectors - catalog gap part-l5p-injector-seal-kit-gap Duramax L5P In-Tank Transfer (Lift) Pump (OEM) part-l5p-lift-pump Duramax L5P Fuel Pump Power Control Module (OEM) part-l5p-lift-pump-controller 6.6L Duramax L5P NOx Sensor, Position 2 / Downstream 2017-2019 (GM 12741484) part-l5p-nox-sensor-downstream-1719 6.6L Duramax L5P NOx Sensor, Position 2 / Downstream 2020-2023 (GM 12747870) part-l5p-nox-sensor-downstream-2023 6.6L Duramax L5P NOx Sensor, Position 1 / Upstream (GM 12718742) part-l5p-nox-sensor-upstream 6.6L Duramax L5P Thermostat (GM 12680457) part-l5p-thermostat Duramax L5P VGT Turbo Actuator (OEM) part-l5p-turbo-actuator Duramax L5P Turbocharger 2020-2023 (OEM) part-l5p-turbocharger Duramax L5P Water Pump (OEM) part-l5p-water-pump

Recipes

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

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Vehicle configurations