Toyota Motor Corp.'s Akio Toyoda, beset by recalls since taking over as president in 2009, is now finding more flaws in one of his most high-profile models and adding to a growing fleet of cars that need fixing.

Toyota said Wednesday that it is recalling about 1.9 million Prius hybrids worldwide, or more than half of those sold since the model's debut 17 years ago. The company is asking its dealers to upgrade the software, which could cause the cars to lose power or shut down and stop.

While the grandson of Toyota's founder has steered Toyota back to prosperity — the company is forecasting record profit this fiscal year — weeding out defects is among the targets that still elude him.