Today Toyota Motor (TM -1.63%) announced vehicle recalls in the U.S., including more than 700,000 Prius vehicles, and approximately 300,000 total Toyota RAV4, and Tacoma models, as well Lexus RX350 vehicles. The recalls are the result of two separate issues, and are all considered to be voluntary safety recalls.

For the affected 2010 to 2014 Prius models -- totaling more than 1.9 million worldwide -- Toyota will upgrade the engine control unit (ECU) which helps governs engine performance to ensure it is operating at the optimal level. The press release noted that "the software's current settings could result in higher thermal stress in certain transistors, potentially causing them to become damaged," and that this could cause the vehicle to shut down entirely, or enter a "failsafe mode."

Toyota said that 997,000 of the affected Prius cars are in Japan, some 713,000 in North America, another 130,000 in Europe, and the rest in other regions.

In addition to the Prius recalls, Toyota will also be issuing recalls for 2012 RAV4, 2012-2013 Tacoma, and 2012-2013 Lexus RX 350 vehicles. The issue with those cars stems also from the ECU, except the problem is one that may cause the vehicle stability control, anti-lock brake, and traction control functions to intermittently turn off. The company did highlight that if the issue does present itself, the braking functions of the vehicles remains fully operational.

Owners of the vehicles in the recall will receive the upgraded software at no cost, and they will receive notification when the upgrades are available at their dealers. The release highlighted Toyota had not received any notifications of accidents or injuries resulting from the issues it is recalling the vehicles for.

-- Material from The Associated Press was used in this report.