Failure mode - Duramax 6.6L V8 Turbo Diesel (GM HD, LML 2011-2016; LGH vans 2011-2016)

EGR valve / cooler carbon and coolant service (LML)

Reliability tier: aggregated - verify before ordering, see /disclosure/

Symptoms

EGR flow codes, hesitation under load
coolant loss traceable to the EGR cooler; carbon buildup at the valve

Compare with the other causes of the same sign on this engine: losing coolant (2 causes) · misfire, rough idle, hesitation or surging (3 causes)

Root cause

Exhaust recirculation deposits carbon at the valve and clogs cooler passages over mileage; cooler internal leaks put coolant into the intake tract. Same EGR-era hardware themes as the LMM, now under DEF-era thermal load.

Diagnosis

command the EGR valve with a bidirectional tool before replacing it
pressure-test the cooling system to separate a cooler leak from other coolant loss

Fixes

replace the EGR valve or cooler as testing dictates ()

egr-valve - more than one option: Duramax LML EGR Valve (OEM), Duramax LML Emission Control Valve, Parallel Chain (OEM)
egr-cooler - more than one option: Duramax LML EGR Cooler 2011-2014, Cab-Qualified (OEM), Duramax LML EGR Cooler 2011-2016 (OEM), Duramax LML EGR Cooler 2013-2016 (OEM), Duramax LGH EGR Cooler, van (12650369)

Prevalence

occasional