Turtle light??

The terms "coolant light" and "been on for a while" should never be used in the same sentence. You should not wait to see how long it will take for this to clear itself.

I would start by checking the voltage of the 12V. So many issues can be be caused by a weak 12V. 12.6 and above is a strong 12V.

These were some comments found on the subject. You don't say where you live or what temperatures you're dealing with but maybe something here will sound familiar. More information about the condition might help to troubleshoot it better.

Turtle Icon

The Turtle light is explained on p. 94 of my old
2001 manual.<br><br>Basically, it's a warning light
stating that the hybrid battery is in some diminished
condition, so your available power will be limited. drive
without hard acceleration, or pull over from that big
mountain that you're climbing, or stop driving in reverse
for that long distance, to allow the battery to warm
up/cool down/recharge.<br><br>The turtle light will come
on briefly when you start up the Prius, but should
go off quickly if all is OK.<br><br>The reviews/test
drive reports of the Japanese-style Prius
(pre-North-American release), which had a smaller battery and engine,
had several reports of the Turtle coming on, mainly
on long uphills and such battery-draining
activities.<br><br>Many people have gone up long mountain ranges and had
the electric assist cut out on them, and not gotten
the Turtle (where it's expected). The only reports of
a US Turtle sighting have been when the Prius sits
outside long in really cold temps (&lt;20F for a long
time), and I think I recall one or two reports in 110+F
degree desert driving. It'll take the Prius a bit longer
to give you the READY light in this instance.

Prius Starts but won't move | PriusChat

 

Short answer: get it to a dealer ASAP for diagnosis. If you are ambitious have them tell you all of the trouble codes that are reported, and post them in the "Gen I" forum.