Francis,
Sorry for not responding sooner.
Our Prius is a 2002 generation-1, quite different from your 2008. The traction battery died 2 years ago (125,000 miles), and Toyota discounted the battery and labor; so I only paid $1,200 (regular cost, $3,000+). Other parts replaced include the coolant pump (2x); belts, hoses, shocks & struts at 120,000 miles, 12-volt battery (2x), and 3 sets of tires.
At 135,000 miles, we expect our Prius to last another 100,000.
In any case, I have not experienced the problem you describe. However, a Google search revealed some items to check:
https://www.google.com/?gws_rd=ssl#q=2008+prius+fail+code+poaa6
Hopefully, this problem has been fixed; and it didn't cost too much.
Good luck. I'd like to hear how your repairs turned out.
Thanks,
Phoenix ("Skip" in Phoenix, AZ)