Electrical System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
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.
- If you cannot hear each solenoid energize and de-energize, then refer to DTC P3401, P3425, P3441, or P3449 .
Mechanical System Testing
- 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.
- Start the engine. Allow the engine to reach normal operation temperature.
- 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.
- 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 .