Toyota Ties 2010 Prius Brake Problem to Lag From Regenerative to Friction Braking
By John O'Dell February 4, 2010Fix Instituted Late Last Month, But Not Yet Applied to 2010 models Already Sold
In a hastily called press conference in Japan this morning, a top Toyota executive said that the company not only was aware of a braking problem with its redesigned 2010 Prius but had instituted a fix late last month without telling customers who'd purchased models built before then.
The admission came as the National Highway Traffic Safety Administration opened a U.S. investigation of the 2010 Prius braking system to determine whether it is plagued by temporary loss of braking power on bumpy roads.
The agency said it has fielded 124 consumer complaints - four involving crashes - that cite that specific issue.
Japan's transportation ministry - which ordered Toyota on Wednesday to begin an investigation of the Prius brake system - has said it has received 38 complaints since July.
Toyota may have just provided an answer: The Prius brake problem is caused by the lag time between the car's regenerative braking system cycling off and the antilock braking system taking over, Toyota Managing Officer Hiroyuki Yokoyama told reporters in Japan.
A report in the trade journal Automotive News this morning quotes Yokoyama as saying that the problem seems to be worst when the car is being driven on bumpy or slippery surfaces, and that complaints in Japan and North America rose in December as cold weather caused icy roads roads in many places and triggered increased use of the cars' friction, or antilock, braking systems.
"When ABS comes into play, you may feel a little bit of slip, but if you continue to apply the brake it will work," Yokoyama said. "It may cause customers a little unease."
He said Toyota updated the Prius' braking control software in late January to reduce the lag time - a fix that may work for cars now coming into the market but that hasn't been applied to the more than 200,000 third-generation Priuses already sold since the model's introduction last summer.
Yokoyama, according to the report, said that Toyota didn't notify customers of the software change and still isn't sure how to apply it to cars that were sold before the fix was developed.
He said that Toyota hasn't determined whether the momentary lag in braking presents a safety hazard.
The Prius brake investigations are separate from the company's massive recall of nearly 5 million cars and trucks to repair a potentially sticky accelerator pedal and from a separate recall of millions of more models - including 2004-2009 model year Priuses (the second-generation of the hybrid) - for a problem associated with loose floor mats jamming the accelerator pedal.
The two acceleration-related recalls and now the 2010 Prius brake probe have severely damaged Toyota's once-stellar reputation of safety and reliability.
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