Cylinder Deactivation System
Description
1. The Cylinder Deactivation System (or Active Fuel Management System) improves fuel economy and lowers emissions by deactivating four of the engine’s eight cylinders (V8 models) or two of the engine’s six cylinders (V6 models). During starting, idling and medium or heavy throttle conditions, the engine operates normally. But during light-load cruising, the Powertrain Control Module (PCM) deactivates cylinders one and seven in the front cylinder bank and cylinders two and four in the rear cylinder bank (V8 models), or cylinder 3 on the right cylinder bank and cylinder 6 on the left cylinder bank (V6 models), effectively turning the engine into a V4.
2. The system consists of the Valve Lifter Oil Manifold (VLOM) assembly and specially designed valve lifters. The VLOM assembly consists of electrically operated solenoids. Each solenoid directs the flow of pressurized engine oil to the special intake and exhaust valve lifters. An oil pressure sensor, which is mounted on the VLOM assembly, monitors engine oil pressure and functions as an information sensor for the PCM. An oil filter, helps control contamination inside the hydraulic circuit of the Cylinder Deactivation System. An oil pressure relief valve, regulates engine oil pressure to the lubrication system and to the VLOM assembly.
3. When operating in normal V6 or V8 mode, the special valve lifters function just like conventional lifters. The solenoids in the VLOM assembly are in their closed position and no pressurized oil is directed to the valve lifters. Spring-loaded locking pins in the lifters extend outward, mechanically locking the pin housings to the outer bodies of the valve lifters.
4. When the conditions are right, the PCM grounds the solenoid control circuits, which allows current to flow through the solenoid windings. When the solenoid windings are energized, the normally-closed solenoid valves open, which directs pressurized engine oil through the VLOM assembly into oil passages in the engine block lifter valley. The pressurized oil forces the locking pins inside the designated lifters inward, locking up the pushrods and preventing them from traveling up and down. The outer bodies of the lifters continue moving up and down independently of the pin housings. Additionally, the PCM turns off the fuel injectors to those cylinders.
5. When the PCM turns off the system, the solenoids in the VLOM assembly close, blocking the flow of pressurized oil to the valve lifters. The oil pressure within the lifters decreases and the locking pins again move out to mechanically lock up the pin housing with the outer lifter body.
Component replacement
Oil pressure sensor and oil filter
6.0L V8 engine
6. Remove the engine cover. On some models it may be necessary to remove the intake manifold (see V8 engines).
7. Disconnect the electrical connector from the oil pressure sensor (see illustration).
19.7 Disconnect the electrical connector from the oil pressure sensor …
8. Remove the VLOM oil pressure sensor (see illustration) and remove the sensor washer.
19.8… unscrew the sensor with a deep socket and remove the sensor and washer …
9. Remove the oil filter and the filter 0-ring (see illustration). If the filter is plugged or the 0-ring is cracked, torn or otherwise deteriorated, replace the filter and 0-ring as a set.
19.9 … then carefully wedge the tip of a screwdriver (A) into the top of the oil filter and pull out the filter. Inspect the condition of the screen and the condition of the 0-ring (B). If either is damaged, replace the filter and 0-ring as a set
10. Installation is the reverse of removal.
4.3L V6 and 5.316.2L V8 engines
Note: The sensor is accessible without removing the intake manifold and fuel rail. The filter may also be accessible by removing the throttle body only.
11. Remove the throttle body (see Fuel and exhaust systems) for access to the oil pressure sensor and VLOM oil filter (see illustration).
19.11 The oil pressure sensor (A) and oil filter (B) are located under the throttle body
12. Remove the sensor by unscrewing from the from the VLOM. Access the filter by removing the plug from the VLOM (see illustration).
19.12 Cylinder deactivation system components (4.3L V6 shown, 5.3L/6.2L V8 V8 similar)
A) Oil pressure sensor
B) Oil filter plug
C) VLOM assembly
D) VLOM solenoid
13. Remove the oil filter plug, sealing ring, then pull out the filter. If the filter is plugged or the 0-ring is cracked, torn or otherwise deteriorated, replace the filter and 0-ring as a set.
14. Installation is the reverse of removal.
Valve Lifter Oil Manifold (VLOM) assembly
15. Refer to V6 engine or V8 engines for the VLOM removal and installation procedure.