Circuit/System Testing

Electrical System Testing

1. Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description .
2. Ignition ON, verify the scan tool hood position parameter displays Open.
   • If the hood position does not display Open, refer to Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.
3. 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

1. Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description .
2. Ignition ON, verify the scan tool hood position parameter displays Open.
   • If the hood position does not display Open, refer to Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.
3. Connect a vacuum gauge to the EVAP vacuum tube fitting on the electronic throttle body. DO NOT use a compound pressure and vacuum gauge. The vacuum gauge on a hand held vacuum pump will work fine for this test.
4. Start the engine. Allow the engine to reach normal operation temperature.
5. 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 .