I would replace the 12 volt battery, 6 years was a good life. http://www.elearnaid.com/opdsopbadifi.html
If you have HID headlights, this is a known issue. http://www.amazon.com/Philips-Xenon-Headlight-Bulb-Pack/dp/B00480J4J6/ref=au_pf_pfg_s?ie=UTF8&Make=Toyota|76&Model=Prius|1026&Year=2006|2006&carId=005&n=15684181&newCar=1&s=automotive&vehicleType=automotive Buy two Search youtube for hints on installation, it is not obvious.