Recipe - Duramax 6.6L V8 Turbo Diesel (GM HD, LML 2011-2016; LGH vans 2011-2016)
Reliability build
Reliability tier: verified - verify before ordering, see /disclosure/
Low-pressure fuel system health for the LML (mode Bosch CP4.2 high-pressure pump failure and fuel-system contamination's prevention side and Piezo injector failures / replacement economics (LML)): the LML has an in-tank lift pump feeding the CP4, and a rail relief valve that opens under overpressure. Keep the low-pressure side healthy, watch for pressure-drop symptoms, and treat any WIF event as an immediate filter change - the CP4's life depends on it.
Parts
- Duramax LML In-Tank Fuel Pump Module, Box-Tank Variant (OEM) - in-tank lift pump module, box-tank variant (13578388) (qty 1)
- Duramax LML In-Tank Fuel Pump Module, Standard-Tank Variant (OEM) - in-tank lift pump module, standard-tank variant (13578389) (qty 1)
- Duramax LML Fuel Injection Pressure Relief Valve (OEM) - rail overpressure relief valve (12611872) - a valve stuck open reads as low rail pressure (qty 1)
- Duramax LML Rail Pressure Sensor (OEM) - rail pressure sensor (12651990) - rule out the sensor before the pump (qty 1)
- Duramax LML Exhaust-Tract Fuel Injector for DPF Regeneration (OEM) - exhaust-tract regen injector (19421482) - failed regens trace here (qty 1)
Install order
- log rail pressure readings (sensor 12651990) - separate sensor lies from pump/valve reality
- relief valve check: a stuck-open valve mimics pump wear at a tenth of the price
- lift-pump module renewal on volume/pressure complaints (variant split by tank/box - verify at order)
- regen failures: check the exhaust-tract injector
Expected outcome
Stable low-pressure supply, honest rail readings, fewer contamination preconditions for the CP4.
Do not
- do not run the low-pressure side to failure - a starved CP4 is a dead CP4
Parts budget
About $100-$280 in parts. It depends on what the diagnosis finds; each option below is what you buy together. Prices marked "at Dave's" are Dave's Auto Center's, the same as in his store; the others are approximate prices from OEM and maker catalogs, rounded (a manufacturer's list price can run higher). Parts only, no labor.