Duramax LML (2011-2016): misfire, rough idle, hesitation or surging

3 documented failures on this engine list this among their signs. They are ordered from the most widespread down. Each one shows the signs in its record's own words, how to tell it from the others, the usual fix and any recall or bulletin.

Bosch CP4.2 high-pressure pump failure and fuel-system contamination Very common · 5 recall/bulletins
EGR valve / cooler carbon and coolant service (LML) Occasional
Piezo injector failures / replacement economics (LML) Occasional

Not sure which engine you have, or want the recalls for your exact truck? Check your VIN: it names the engine and lists the campaigns for that model year. Whether a recall is still open on your VIN: nhtsa.gov/recalls.

1 Bosch CP4.2 high-pressure pump failure and fuel-system contamination

verified How widespread: Very common

How it shows up

sudden loss of power / rough running, then a no-start as rail pressure collapses

Its other signs

metal shavings in the fuel filter housing; the CP4's internal cam/c-roller wears through and sends debris down the high-pressure lines into the rails and injectors
repair bills owners report at $7,000-$17,000 (NHTSA complaints 2016-2025): the documented outcome is a full tank-to-injector fuel system replacement, not just a pump

How to tell it apart

cut open the fuel filter first: metal particles = CP4 cascade, stop cranking
quantify rail pressure complaints (crank-no-start after a running event is the classic signature) before spending on injectors
any pump replacement on a contaminated system must be paired with full-system decontamination - lines, rails, injectors, tank

Usual fix

full fuel-system decontamination (tank, lines, CP4 replacement, rails, injectors); the only reliable repair once metal is downstream

Recalls and bulletins

PIE0523 (A, B)PIP4949D / PIP4949E PIP5133 (A-D)PIP5151 (A-F)PIP4949B

Root cause, parts and sources →

2 EGR valve / cooler carbon and coolant service (LML)

aggregated How widespread: Occasional

How it shows up

EGR flow codes, hesitation under load

Its other signs

coolant loss traceable to the EGR cooler; carbon buildup at the valve

How to tell it apart

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

Usual fix

replace the EGR valve or cooler as testing dictates

Root cause, parts and sources →

3 Piezo injector failures / replacement economics (LML)

aggregated How widespread: Occasional

How it shows up

injector balance/contribution codes, rough idle, fuel dilution of oil
hard starting after sitting; one-cylinder miss under load

How to tell it apart

read injector balance rates per cylinder with a scan tool before ordering
a return-flow/balance test separates electrical from mechanical injector faults

Usual fix

replace failed injectors (high-cost item; verify per-card revision windows inside 2011-2016)

Root cause, parts and sources →

Other symptoms on the Duramax LML (2011-2016)

Hard start, long crank or no-start Loss of power, limp mode or derate Losing coolant Ticking, knocking, rattle or whine DEF, DPF and regeneration warnings

Everything on the Duramax LML (2011-2016)Its recalls and bulletins

Order: how widespread each failure is in its record (near-universal, very common, common, occasional, rare), then the number of NHTSA owner complaints that match its keywords. Complaint counts are keyword matches, not a manual review of each complaint. A symptom listed here means the failure is documented with that sign; it is not a diagnosis of your truck. Tiers: verified, aggregated, contested, data-gap. How we tier and source facts.