To provide maximum fuel economy under light load driving conditions, the engine control module (ECM) will command the valve lifter oil manifold (VLOM) solenoids ON, to deactivate engine cylinders 1, 3, and 5. The VLOM consists of 3 electrically operated normally closed solenoids, which directs pressurized engine oil to 6 deactivating valve lifters. All 3 VLOM solenoids are connected in parallel to a fused ignition circuit supplied by the powertrain relay. The control circuit for each solenoid is connected to an individual low side driver internal to the ECM. When enabling conditions for V3 mode are met, the ECM will command the low side driver to turn ON, in engine firing order sequence

The valve lifter oil manifold (VLOM) solenoids are assigned to the following engine cylinders:

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cylinder Deactivation (Active Fuel Management) System Description

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. If any DTCs are set, then repair those DTCs first. Refer to Diagnostic System Check - Vehicle .

⇒	If sent here from P0300, continue with testing.

2. Start and idle the engine.
3. Allow the engine to reach normal engine operating temperature. The engine should idle smoothly, without any misfires.
4. Monitor the cylinder deactivation system data parameters with a scan tool.
5. Road test the vehicle under light throttle and load conditions that will allow the engine control module (ECM) to command V3 mode. If all enabling conditions are met for cylinder deactivation, and if no internal engine hydraulic/mechanical fault conditions are present, the ECM will continue with V3 mode operation.

⇒	If the vehicle passes the Circuit/System Verification Test, then review the active fuel management driving information in the Features and Controls section of the owners manual with the vehicle operator, or instruct the vehicle operator in the proper driving techniques to obtain V3 mode.

⇒	If the vehicle does not pass the Circuit/System Verification, then review the cylinder deactivation inhibit reasons listed on the scan tool.

Electrical System Testing

Ignition ON, engine OFF, command each valve lifter oil manifold (VLOM) solenoid ON, and OFF, using the scan tool. Standing next to the engine compartment, you should be able to hear the solenoids energize, and de-energize with each command.

Mechanical System Testing

Important: DO NOT drive vehicle during this test.

1. Connect a vacuum gage to the brake booster fitting at the upper intake plenum. Do not use a compound pressure and vacuum gage. The vacuum gage on a hand held vacuum pump will work for this test.
2. Start the engine. Allow the engine to reach normal operating temperature.
3. Command each VLOM solenoid ON, one at a time. Each time a solenoid is commanded ON, you should observe a fluctuating drop of intake manifold vacuum, a rough idle, and a misfire on the cylinder that was deactivated.

⇒	If there is no fluctuating drop in engine vacuum, or the engine does not misfire, then refer to Cylinder Deactivation (Active Fuel Management) System Compression Test .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.