Tahoe 4WD V8-5.3L (2007)
Valve Deactivation Solenoid: Testing and Inspection
CYLINDER DEACTIVATION (ACTIVE FUEL MANAGEMENT) SYSTEM DIAGNOSIS
DIAGNOSTIC FAULT INFORMATION
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and Diagnostic
Overview/Diagnostic Starting Point - Vehicle
CIRCUIT DESCRIPTION
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 and 7 on the left bank, and cylinders 4 and 6 on the right bank. The VLOM consists of 4
electrically operated normally closed solenoids, which directs pressurized engine oil to 8 deactivating valve lifters. All 4 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 V4 mode are met, the ECM will command the low side driver to turn ON, in engine
firing order sequence.
DIAGNOSTIC AIDS
The VLOM solenoids are assigned to the following engine cylinders:
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Solenoid #1-Cylinder #1
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Solenoid #2-Cylinder #4
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Solenoid #3-Cylinder #6
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Solenoid #4-Cylinder #7
CIRCUIT/SYSTEM VERIFICATION
1. If any DTCs are set, then repair those DTC first.
2. Start and idle the engine.
3. Allow the engine to reach normal engine operating temperature. The engine should idle smoothly without any misfires. If the engine misfires, refer
to DTC P0300 - P0308. See: Testing and Inspection/Diagnostic Trouble Code Tests and Associated Procedures/P Code Charts/P0300 See:
Testing and Inspection/Diagnostic Trouble Code Tests and Associated Procedures/P Code Charts/P0308
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 ECM to command V4 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 operation in V4 mode.
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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 V4
mode.
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If the vehicle does not pass the Circuit/System Verification test, then review the cylinder deactivation inhibit reasons listed on the scan tool.
CIRCUIT/SYSTEM TESTING
Electrical System Testing
Ignition ON and the engine OFF, command each VLOM solenoid ON and OFF using the scan tool. Standing next to the engine compartment, you
should be able to hear the solenoid energize and de-energize with each command.
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If you cannot hear each solenoid energize and de-energize, then refer to DTC P3401, P3425, P3441, or P3449. See: Testing and
Inspection/Diagnostic Trouble Code Tests and Associated Procedures/P Code Charts/P3401 See: Testing and Inspection/Diagnostic Trouble
Code Tests and Associated Procedures/P Code Charts/P3425 See: Testing and Inspection/Diagnostic Trouble Code Tests and Associated
Procedures/P Code Charts/P3441 See: Testing and Inspection/Diagnostic Trouble Code Tests and Associated Procedures/P Code
Charts/P3449
Mechanical System Testing
1. Connect a vacuum gage to the EVAP vacuum tube fitting on the electronic throttle body. DO NOT use a compound pressure and vacuum gage.
The vacuum gage on a hand held vacuum pump will work fine for this test.
2. Start the engine. Allow the engine to reach normal operation temperature.
3. With a scan tool, command each VLOM solenoid ON, one at a time. Each time a solenoid is command ON, you should observe a fluctuating
drop of intake manifold vacuum, and a misfire on the cylinder that was deactivated.
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If there is no fluctuating drop in engine vacuum, or the engine does not misfire, then refer to Cylinder Deactivation (Active Fuel
Management) System Diagnosis.
REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. See: Testing and Inspection/Diagnostic Trouble Code Tests
and Associated Procedures/Verification Tests and Procedures
