Chevrolet Silverado / GMC Sierra. Service manual — part 1892

not running and no engine oil pressure to the CMP actuator, the high tension spring positions
camshaft timing at the 17 degree advanced park position. During normal engine operation and
based on performance requirements, the ECM may adjust camshaft timing, as required, within a
range from 17 degrees advanced to 45 degrees retard.

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. 40: Timing Camsghaft - 52 Degree Range Of Authority
Courtesy of GENERAL MOTORS CORP.

The 6.0L LY6 CMP actuator has a 52 degree range of authority. With the engine not running and

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

no engine oil pressure to the CMP actuator, the high tension spring positions camshaft timing at
the 7 degree advanced park position. During normal engine operation, and based on performance
requirements, the ECM may adjust camshaft timing, as required, within a range from 7 degrees
advanced to 45 degrees retard.

CMP System Lubrication Flow and Actuator Operation

Fig. 41: Cutaway View Of Actuator
Courtesy of GENERAL MOTORS CORP.

1. Oil enters the camshaft at the second main bearing journal (1).

2. Oil travels through the camshaft into the CMP actuator valve check ball (2) and filter (3).

3. Oil exits the valve and travels through the internal passages of the camshaft (4).

4. Oil exits the camshaft and enters the actuator oil entry ports.

5. Oil travels through the actuator and is directed back into the valve (5).

6. Valve spool position directs oil to the advance or retard passages of the actuator.

The valve may also, under certain conditions, be positioned in a neutral position with no flow to
either the advance or retard passages of the actuator.

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. 42: Identifying Actuator Passages
Courtesy of GENERAL MOTORS CORP.

1. Oil flows from the camshaft into the valve inlet (3) through the internal check ball and filter.

2. Oil exits the valve (2) and travels within the internal passages of the camshaft into the entry

ports (7) of the actuator.

3. The center oil groove of the actuator is pressurized and oil reenters the valve (1).

4. Valve spool position directs oil out of the valve advance (5) or retard (4) ports to the

actuator.

The valve may also, under certain conditions, be positioned in a neutral position with no flow to
either the advance or retard passages of the actuator.

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