According to Toyota, the ABS system found in its hybrid models should under normal conditions engage and disengage many times per second as it reacts to tire slippage, but for the 2010 Prius, Toyota Sai and Lexus HS 250h hybrids the system can fail to engage at the proper rate while braking over pot holes or uneven surfaces.
Toyota had made a change on the production line for the 2010 Prius once it learned of this problem back in late January, but the vehicles produced prior to that date will require a software upgrade in order to fix the problem. The Lexus HS 250h is still being produced without a fix, but the Lexus HS 250h and Toyota Sai will have their sales halted until a fix is in place, according to CNN. Toyota says that it will implement a change on the production line later this month.
According to NHTSA reports, the 2010 Prius has logged more than twice as many complaints than the sum of all other 2010 Toyota models combined - including the models included in the latest recalls.
Toyota also says that it will begin mailing letters to Prius owners included in this recall next week and HS 250h owners within the next few weeks. The affected vehicles in the U.S. will need to have a re-flash of the car's computer in order to fix the issue.