The warning light that alerts you to light bulb failure stays on even though all exterior lights are working. The only light in the whole car that is burnt out is the one at the tip of the pass. side mirror control, could this be the problem?

Check the third brake light. Often it gets overlooked.

"Check the third brake light. Often it gets overlooked."

Didn't even think about it, I'll check it. Thanks

If it is the third brake light the warning light should only come on when you apply the brakes. The system is only supposed to tell you a light is not working when you try to turn that light on (when you operate the brake). There are small marker lights at each rear corner that should be on whenever you turn the headlights on. It is difficult to see these lights are even on when the sun is out. Check those out too.

thanks for all of your ideas. I've checked everything including the possibility of a dim headlight but the light remains on. Could the power mirror light failure cause the warning light to be on?

Bulb failure warning
 

the mirror will not cause this warning to illuminate. As one of the other post said check the rear side markers. Sometimes bulbs of different manufactures will cause this problem even if the bulbs look ok. By this I mean bulbs of different makes side to side installed the car. the fix is usually to replace all the bulbs with bulbs from the same package.(I'm talking about taillights). Only the exterior lights will turn the bulb warning light on. Clues to help diagnoses; key on, watch for warning light,Press brake pedal- Brake light bulb, parking light only on- parking light bulb, headlights same thing ,you get the picture. Good Luck,Brian

Do what shooter said, make sure all bulbs are the same wattage.
Also, check the license plate lights and the fuse box.