I had a similar problem with the overheat light flashing. I turned the car off and back on, it was gone. I didn't check the collant though. Mine is a '97, is it air or water cooled. The site mrmickeymouse posted says they only '99-up are water cooled. But 986faq.com says '97-up are water cooled.
http://www.986faq.com/2-0/stdequip.asp