From the previous posts on this subject, it has become apparent that the 3rd generation Prius, starting with the 2010 model, has issues when braking. It seems that on slippery or bumpy surfaces, a loss of braking can occur. In a move that is no longer shocking for Toyota, it appears that they knew about the issue and didn’t tell anyone until it became news earlier this week. Hiroyuki Yokoyama, Toyota’s manager of Quality Control, told the New York Times that they had fixed the issue and any 2010 model year Prius sold since late January has the fix built in. No specific date was mentioned, but expect when a recall is announced. While Toyota has yet to confirm a recall, I highly doubt they can let this one go without announcing another recall.
The problem stems from the way a Prius is slowed. Hybrids have both friction and regenerative braking systems. The former is the same as on traditional cars, while the latter uses the car’s momentum to slow itself and charge the hybrid battery pack at the same time. Regenerative braking is used because it makes use of normally wasted energy. HowStuffWorks has a great article on this, if you want more details on the subject.
With these dual braking systems, the car’s on-board computer has to take the driver’s input and divide it between the two braking systems. This brake controller is where the 2010 Prius’ problem is, causing a momentary lack of braking power while it switches between the two systems. On less-than-ideal road surfaces, be it weather or potholes, this can lead to accidents. Normal braking for a stop light probably wouldn’t cause an accident, even experiencing the lack of brakes, because most people give themselves plenty of room to stop. When the driver isn’t anticipating a lack of brakes, this issue could lead to an accident.
So why is this a problem with the 2010 Prius and not the 2003-2009 models sold in the US? According to Toyota, the 2010 Prius uses a different regenerative brake system than its predecessors. Also, the complaint count for the 2010 Prius is up to 124, with 4 known crashes in the United States, and Automotive News is reporting that the NHTSA is officially looking into the problems with the brakes on 2010 Prius cars.
Whenever new information is known, I’ll have an update for you.
by John Suit
Sources: New York Times, Automotive News