loose yellow wire

I found a loose yellow wire of fairly heavy gauge when changing the oil on my newly purchased 97 bonneville SE. The wire originates at the firewall, coming through a grommet immediately behind the driver side shock tower along with a red wire. The wire is long enough to reach the front of the engine, and has 12volts on it when the engine is running. I have been looking for something missing a wire but have not had any luck yet. Could someone take a look under their hood and see if they have the same wire, and where it runs to?

Thanks a million!:grinyes:

Sounds like a cable for an aftermarket sound system to me.