Toyota 2013 Prius Owner's Manual page 557

5-2. Steps to take in an emergency
Stop the vehicle immediately.
The following warning indicates the possibility of damage to the vehi-
cle that may lead to an accident. Immediately stop the vehicle in a
safe place and contact your Toyota dealer.
Warning light
534
PRIUS PHV_OM_OM47787U_(U)
Warning light/Details
Charging system warning light
Indicates a malfunction in the vehicle's charging system
High coolant temperature warning light
Indicates that the coolant temperature is too high
Changes from a flashing to a solid light when the engine
coolant temperature increases.