Ant-Man

I don't know anyone around with a C6, and I couldn't find any matching place to plug it into.. it's right by the passenger fog light.

It's most likely painfully obvious but I only get to see the car a few hours a week or I'd keep looking.

User Omega

I believe this is the plug for the under hood light that some models had a wiring provision for but did not come with the light.

Unreal

Underhood light.

My 06 had a hood light, but I think they stopped it later, but kept same harness so plug is still there.