Circuit/System Verification

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description .
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.
Verify that no other DTCs are set.
- If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
Engine idling, verify there is no abnormal engine noise.
- If there is an abnormal engine noise, refer to Symptoms - Engine Mechanical .
Observe the Misfire Current Counters with a scan tool. The Misfire Current Counters should not be incrementing. A random misfire, across one or more cylinders that are not steadily incrementing may be normal for this engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.