Faulty software in Toyota's popular Prius hybrids has forced the Japanese automaker to recall 1.9 million of such vehicles worldwide. The huge recall—representing more than half of all Prius cars ever sold—shows how Toyota has adopted an increasingly cautious stance as major automakers struggle with the rise of software-related car problems.
The flawed Prius software can cause overheating and damage in transistors within the electronic system controlling the hybrid's gasoline-electric hybrid motor, according to The Wall Street Journal. That scenario can trigger warning lights on the dashboard and force the vehicle into a failsafe mode known as "limp home mode" that slows vehicle performance to a crawl. In "rare circumstances," Toyota warned that the hybrid system might shut down and bring the vehicle to a halt while it's being driven.
Another Wall Street Journal article reported that Toyota has received 451 reports of this particular software problem since May 2011. Toyota's subsequent recall covers all of the newest, third-generation Toyota Prius hybrids that have been produced since 2009. Almost 1 million of the recalled vehicles are in Japan, 700 000 are in the United States, and 130 000 are in Europe.
Toyota also announced a separate recall to update the skid control software for a combined 295 000 vehicles of other Toyota models: 2012 RAV4 sport utility vehicles, 2012-2013 Tacoma pickup trucks, and 2012-2013 Lexus RX 350 SUVs.
The Prius recall signifies the latest case in possible software-related problems for major automakers. Many modern cars use dozens of electronic control units (ECUs) and tens of millions of lines of software code—a scenario that will likely become even more complex as Toyota and other automakers move toward semi-autonomous or even fully autonomous self-driving car systems. Such complexity leaves plenty of room for more software glitches and bugs that could lead to costly recalls and potentially lawsuits.
Toyota has more than enough experience by now in learning how to address such issues. The automaker is still dealing with a 2009 controversy over sudden unintended acceleration (SUA) that sparked an initial recall of 3.8 million vehicles, as readers of IEEE Spectrum'sRisk Factor blog will know. Toyota has consistently argued that such incidents stem from driver error rather than any faulty vehicle electronics, but its lawyers recently took steps toward allowing for a broad settlement agreement.
In any case, Japanese investors seemed to view Toyota's latest recall without alarm as Toyota's stock ended up 0.4 percent after the announcement.
"My impression is Toyota is recalling more often, even with very minor flaws" with its vehicles, said Yuuki Sakurai, the Tokyo-based president of Fukoku Capital Management Inc., in a Bloomberg Businessweek interview. "Toyota learned its lesson from the big recalls in 2009 and 2010."
Jeremy Hsu has been working as a science and technology journalist in New York City since 2008. He has written on subjects as diverse as supercomputing and wearable electronics for IEEE Spectrum. When he’s not trying to wrap his head around the latest quantum computing news for Spectrum, he also contributes to a variety of publications such as Scientific American, Discover, Popular Science, and others. He is a graduate of New York University’s Science, Health & Environmental Reporting Program.