Visual/Physical Inspection

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

Inspect for aftermarket devices which can affect the operation of the power outlets. Refer to Checking Aftermarket Accessories
Inspect the accessible system components or the visible system components for obvious damage or for obvious conditions which can cause the symptom.