The Japanese automaker has advising the National Highway Traffic Safety Administration (NHTSA) that it's to recall affected Prius models to rectify software in two of the Prius's electronic control units, one for the motor/generator and the other controlling the hybrid system.
Toyota says the current settings could result in "higher thermal stress in certain transistors", potentially causing them to become damaged.
If this occurs, the company says various warning lights may illuminate, and the vehicle would revert to a failsafe mode.
In rare circumstances, it could shut down the hybrid system itself, "resulting in loss of power and the vehicle coming to a stop".
Toyota says it has received no reports of accidents or injuries related to the problem, which affects 1.9 million Prius models globally.
Owners of affected vehicles will be contacted by first class mail when the software update is available at their dealers. Updates will be carried out free of charge.
Around 260,000 Model Year 2012 Toyota RAV4, 2012-2013 Toyota Tacoma, and 2012-2013 Lexus RX 350 vehicles are being recalled for a separate ECU issue, to fix an issue that can cause the Vehicle Stability Control, Anti-lock Brake, and Traction Control functions to intermittently turn off.
Once again, no accidents or injuries have been reported, and Toyota will again contact owners for their free update when it becomes available.
Toyota owners wishing to know more can contact the company at toyota.com/recall or by calling the Toyota Customer Experience Center at 1-800-331-4331. Lexus owners can call the Lexus Customer Satisfaction Center at 1-800-25-LEXUS (1-800-255-3987) or head to lexus.com/recall.