Toyota's latest woes may be hard-wired
As the world's largest automaker recalls millions of cars to replace sticky accelerator pedals, safety questions arise related to car electronics.
On top of mounting criticism of mechanical glitches in its, Toyota faces a much more complex set of issues related to electronics, based on consumer complaints and analysis by an electronics engineer familiar with Toyota's history of throttle control.
This comes as political problems continued to pile up for the company, in the wake of of its--including recent Camrys, Corollas, and RAV4s--because of potential acceleration problems and its subsequent halt of production on the affected models.
The U.S. Department of Transportation upped the pressure on Toyota when the agency's head, Secretary of Transportation Ray LaHood, told owners of recalled vehicles to stop driving them during remarks he made Wednesday before a House appropriations hearing. He later backed away from this statement and said he meant only that Toyota owners who are worried about their cars should take them to dealerships.
And in Japan on Wednesday, authorities told Toyota to investigate reports of faulty brakes on its high-profile Prius hybrid car as federal safety regulators in the U.S. began a broader investigation into Toyota's electronic systems.
The Prius also came under scrutiny this week after Apple co-founder Steve Wozniakbecause of an alleged "software" glitch.
Wozniak's claim, valid or not, underscores questions about Toyota's electronic systems raised by less-famous consumers. In a well-documented case detailed in a petition to the National Highway Transportation Safety Administration (NHTSA), Jordan Ziprin claims that, in 2005, when backing out of a driveway near his home in Phoenix, his 2002 Toyota Camry XLE suddenly accelerated and slammed into a utility box.
He did not have his foot on the gas pedal and the car accelerated under its own accord, Ziprin claims. This appears to be an electronic glitch: an issue very different from the mechanical defects cited in the accelerator pedal cases that Toyota is trying to address now with its recall.
"The problem began with 2002 Toyota and Lexus vehicles," Ziprin said in a phone interview. "That was the year that Toyota introduced electronic throttle control," he said. (Toyota introduced it selectively prior to 2002, but first used it on a large scale in 2002.) Reports of unintended acceleration jumped after drive by wire systems were adopted, according to a review by the Los Angeles Times of thousands of consumer complaints filed with the NHTSA.
Toyota, at least publicly, is saying that it has found no evidence of electronic problems. "We have not found any evidence of an electronic problem that would have led to unwanted acceleration," said John Hanson, national manager of environmental safety and quality in Toyota's communications group. "That doesn't mean that we've written it off. We are aggressively investigating any claims."
Hanson continued. "NHSTA over many years of investigation on a wide variety of complaints has found no evidence of any electronic problem with the electronic control system. That doesn't mean it's not possible. We're not ruling out any possibility. And we continue to investigate actively."
The birth of drive-by-wire
At the center of the alleged incidents is the electronic throttle control, or what is more generally referred to as "drive by wire." This was seen as a significant leap in automotive technology for car makers like Toyota, replacing the traditional mechanical and hydraulic control systems with electronic control systems.
Drive by wire allows for a more refined, computer-controlled acceleration and, somewhat ironically--at least to some owners with problem-plagued cars--is thought to boost safety. But it also introduced a new set of hard-to-trace problems, according to Antony Anderson, an engineer and electrical engineering consultant who is familiar with Ziprin's case.
"These are intermittent failure modes. The moment you switch off the (car's) computer, they go away. The problem is that when they look for the errors afterward, there's nothing to be seen," Anderson said. And indeed this is what often happens; the car accelerates and slams into something, disabling the car and leaving no evidence of what caused the electronic glitch, he said.
"In some cases, you may get a fault code showing but often the software hasn't been designed to pick up particular faults and you can't guarantee that you're going to pick up particular faults anyway," he said.
One of the most disturbing aspects of these hard-to-detect glitches is that the driver and other victims often provide the only evidence that something has gone wrong. "What happens today is that the driver is made the fail safe for the electronics," Anderson said.
More technology, more complexity
Today, cars can have as many as 70 electronic control units, or ECUs, based on microcontrollers (sometimes generically referred to as microprocessors). ECUs manage engines, doors, transmissions, seats, and entertainment, and climate systems.
Electronic throttle systems use an array of sensors, microcontrollers, and electric motors to control how the car is accelerated. Gone are the old steel cables to connect the driver's foot to the engine.
Because of all of this added complexity and the need for chips to talk to each other, a bus system was introduced--not unlike the Peripheral Component Interconnect, or PCI bus used in virtually all PCs today. Called the Controller-area network, or CAN-bus, it is designed to allow microcontrollers and devices to communicate with each other within a vehicle.
"It was getting so complicated that they had to go over to a bus system," Anderson said.
So in a sense, the pre-electronic days, in pure technological terms, was a primitive era for cars. More crude, but also more simple. In pre-electronic days, when the driver exercised direct control on the throttle by means of the accelerator pedal, the mechanical arrangement "worked reasonably well most of the time," according to Anderson. "There were certainly cases of stuck-shut throttles and stuck-open throttles caused by excess friction in some part of the system or another. However, an uncommanded wide open throttle was almost an impossibility," he said.
The electronic throttle changed the dynamics between the driver and the car and introduced the possibility of uncontrollable acceleration. "When the driver presses down the accelerator pedal it sends an electrical signal--think of it as a request, not a command--to the ECU 'asking' that the throttle be opened to the required degree determined by the pedal angle," Anderson said. "The ECU takes this input from the accelerator pedal, along with all sorts of other inputs, computes a desired throttle angle and, as it were, instructs the throttle servo to open the throttle to that computed position. Feedback from the throttle position sensor to the ECU closes the loop."
So, here's the crux of the problem, according to Anderson. "The driver is now one stage removed from the actual control process--no longer in direct command of the throttle plate. We have introduced the possibility of what I call 'electronic disobedience' by introducing a computerized system between the driver and the throttle and everything now depends on the integrity of that electronic system," he said.
Which, of course, can sometimes break down due to gremlins like electronic interference. "Although the chance of an intermittent electronic malfunction leading to a sudden acceleration may be very small in any particular vehicle, when considering a population of millions of vehicles the chance of any one of them having a sudden acceleration may be quite high," he said. "One of these problems is an uncommanded wide open throttle that the driver has no means of controlling."
After almost five years, Camry owner Ziprin is still waiting for Toyota and NHTSA to provide some kind of explanation for his crash. After filing a petition with NHTSA in July of 2005, the agency denied the petition in December of that year. "They said that the evidence was ambiguous. The answer that was clearly implied was that it was the driver's fault. That was absolutely ridiculous," he said. Moreover, Toyota, after investigating his claims, ultimately did nothing, he said.