Chevrolet Silverado / GMC Sierra. Manual — part 1890

Courtesy of GENERAL MOTORS CORP.

When operating in V8 mode, the active fuel management valve lifters function similar to the non-
active fuel management valve lifters. The active fuel management oil manifold solenoids are in
the closed position, with no pressurized oil directed to the valve lifters. The pushrod (1) travels
upward and downward to actuate the rocker arm and valve. The spring loaded locking pins (5) of
the lifter are extended outward and mechanically lock the pin housing (4) to the outer body of the
valve lifter (3).

When the active fuel management system is commanded ON, the ECM will direct the solenoids
of the oil manifold to open and direct pressurized oil to the valve lifters. Oil travels through the
valve lifter oil manifold and engine block oil galleries and enters the inlet port (6) of the valve
lifter.

When operating in V4 mode, pressurized oil forces the locking pins (11) inward. The pushrod (7)
remains in a constant position and does not travel upward and downward. The outer body of the
lifter (9) moves upward and downward independently from the pin housing (10). The valve lifter
spring (8) retains tension on the valve train components to eliminate valve train noise.

When the active fuel management system is commanded OFF, the ECM directs the solenoids of
the oil manifold to close, stopping the flow of pressurized oil to the valve lifters. The oil pressure
within the lifter will decrease and the locking pins will move outward to mechanically lock the
pin housing and outer body.

Engine Block

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Fig. 33: DOD Engine Block
Courtesy of GENERAL MOTORS CORP.

The active fuel management engine block incorporates additional features to support active fuel
management system operation. Engine oil pressure is routed to the valve lifter oil manifold
assembly from an oil gallery (2) in the rear of the cylinder block. Cylinders 1, 4, 6, and 7 each
have 2 vertical, cast-in-block oil passages (1). The vertical oil passages permit oil flow from the
manifold assembly to the valve lifter bores.

Engine Control Module (ECM)

Refer to Cylinder Deactivation (Active Fuel Management) System Description .

CAMSHAFT POSITION ACTUATOR AND SOLENOID VALVE DESCRIPTION

Camshaft

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Fig. 34: Camshaft Lubrication Path
Courtesy of GENERAL MOTORS CORP.

The camshaft is designed to provide a lubrication path for pressurized engine oil to flow to the
camshaft position (CMP) actuator. Pressurized engine oil enters the camshaft at bearing journal
location number 2. Oil travels through the camshaft, out the front, and into the CMP actuator
solenoid valve.

CMP Actuator Solenoid Valve

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Fig. 35: CMP Actuator Solenoid Valve Components
Courtesy of GENERAL MOTORS CORP.

The CMP actuator solenoid valve consists of a housing, spool valve (1), spool return spring (2),
oil filter (3), inlet check ball return spring (4), and inlet check ball (5). Pressurized engine oil
enters the valve and travels through the filter to the spool. Spool position is controlled by the
CMP magnet and engine control module (ECM). When the spool is moved to the proper position,
oil flow is directed through the valve and into the CMP actuator assembly. The CMP solenoid
valve is a torque-to-yield design and should be replaced each time it is removed.

CMP Actuator Magnet

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado