(x16) Units Needed for Complete Set
The GM 12645725 (often an ACDelco part) is an Active Fuel Management (AFM) / Displacement on Demand (DOD) valve hydraulic roller lifter. It is designed to fit specific GM V8 and V6 engines (4.3L, 4.8L, 5.3L, 6.0L, and 6.2L) equipped with AFM.
Silverado 1500: 2007–2021 (4.3L, 5.3L, 6.0L, 6.2L)
Tahoe: 2007–2021 (5.3L, 6.0L, 6.2L)
Suburban 1500: 2007–2021 (5.3L, 6.0L, 6.2L)
Avalanche: 2007–2013 (5.3L, 6.0L)
Camaro: 2010–2022 (6.2L V8)
Corvette: 2014–2022 (6.2L V8)
Impala: 2006–2009 (5.3L)
Monte Carlo: 2006–2009 (5.3L)
Caprice: 2011–2013 (6.0L)
Sierra 1500: 2007–2021 (4.3L, 5.3L, 6.0L, 6.2L)
Yukon / Yukon XL: 2007–2021 (5.3L, 6.0L, 6.2L)
Envoy: 2005–2009 (5.3L)
Savana 2500 / 3500: 2009 (4.8L)
Escalade / Escalade ESV / EXT: 2007–2014 (6.0L, 6.2L)
CTS: 2009–2018 (V8 models)
LaCrosse / Allure: 2008–2009 (5.3L)
Rainier: 2005–2007 (5.3L)
Pontiac G8: 2008–2009 (6.0L GT)
Pontiac Grand Prix: 2006–2008 (5.3L GXP)
Saab 9-7X: 2006–2009 (5.3L)
General Motors part 12645725 is the Active Fuel Management (AFM) Valve Lifter Oil Manifold (VLOM) assembly (often called the "valley plate"), which sits beneath the intake manifold on GM V8 engines. It acts as the electro-hydraulic control center that triggers cylinder deactivation.
How the VLOM Activates AFM
The VLOM utilizes a network of solenoids and oil channels to control the specialized, collapsible AFM lifters on specific cylinders.
Computer Request: When driving under light-load conditions, the Engine Control Module (ECM) initiates the AFM system to switch to V4 mode.
Solenoid Activation: The ECM sends an electrical signal to energize four normally-closed electronic solenoids housed in the 12645725 manifold.
Pressurized Oil Routing: When the solenoid opens, it redirects pressurized engine oil through specific internal passages (galleries) to the AFM valve lifters on cylinders 1, 4, 6, and 7.
Lifter Collapse: The sudden surge of oil pressure (typically 22 to 65 psi) unlocks small, spring-loaded latching pins inside the AFM lifters. This decouples the lifter's outer body from its internal plunger.
Deactivation: The lifter collapses inward and simply absorbs the motion of the camshaft. The intake and exhaust valves stay completely shut, and no fuel is injected into those cylinders.
When you press the gas pedal and engine load increases, the ECM de-energizes the solenoid. The oil pressure drops, allowing internal springs to push the locking pins back into place, "pumping up" the lifters and restoring V8 mode
