2010 Toyota Prius Owners Manual - Page 544

5-2. Steps to take in an emergency Interior buzzer Exterior buzzer Warning message Details The electronic key does not operate properly. Correction procedure Once ⎯ (Flashing) →P. 542 ⎯ ⎯ Power was turned off due to the automatic power off function. Next time when starting the hybrid system, increase the engine speed slightly and maintain that level for approximately 5 minutes to recharge the battery.