Sudden Acceleration: Electronic Interference a Possible Cause

Could unintended acceleration, in Toyotas and other makes, be caused by electronic interference with modern cars' sophisticated "throttle by wire" systems? Although there's no smoking gun, it's impossible to rule it out, as both Toyota and the National Highway Traffic Safety Administration (NHTSA) have done.

Late Tuesday, NHTSA said it was investigating electronic interference as a cause of unintended acceleration.

In a 2008 report after testing on a 2007 Lexus ES-350, NHTSA reported, "Multiple electrical signals were introduced into the electrical system to test the robustness of the electronics against single point failures due to electrical interference. The system proved to have multiple redundancies and showed no vulnerabilities to electrical signal activities."

But the report adds, "Magnetic fields were introduced in proximity to the throttle body and accelerator pedal potentiometers and did result in an increase in engine revolutions per minute (RPM) of up to approximately 1,000 RPM, similar to a cold-idle engine RPM level."

It's unclear how this increase in engine speed is reconciled with the "no vulnerabilities" statement. A call to NHTSA seeking clarification was not returned.

According to Clarence Ditlow, the longtime director of the Washington-based Center for Auto Safety, who obtained some NHTSA documents through a Freedom of Information Act request, "Basically, NHTSA didn't do any study. They can't explain what they did--they don't know what they did."

Ditlow said that Toyota vehicles carry an electronic data recorder that, although it stores information for only the most recent time periods, could perhaps shed light on the cause of unintended acceleration cases.

The basic problem is that electronic malfunctions do not necessarily leave a trail of evidence. "It's a classic case of dead men tell no tales," said Ditlow. There is no imprint due to electronic failure." As an example of electronic interference, Ditlow cited a voltage spike generating electromagnetic flux and interfering with the signal sent to the accelerator pedal. He said that, in one incident, a cell phone signal caused a German-made bus to shift into gear.

There is, after all, a reason that passengers are told to turn off portable electronics during aircraft takeoff and landing. According to an IEEE Spectrum article entitled "Do Portable Electronics Endanger Flight?" by Tekla S. Perry and Linda Geppert, "Can a computer or other [portable electronic device] PED, in the right place, on the right airplane, seriously affect the airplane's instrumentation or communications? You bet."

The authors quote Finbarr O'Connor, electromagnetic compatibility manager of R&B Enterprises (and a member of a nonprofit investigating PED problems on planes): "If it were up to me, I would shut PEDs down, period. I would feel better if they were not allowed in the passenger compartment at all. They should be stowed. The potential for them to be turned on accidentally is high. I have no doubt that PEDs have the potential to affect avionics."

NHTSA's report does made it plain that accelerator pedals could "easily" get entrapped in the car's all-weather floor mats. And it reported that 59 of 600 Lexus ES-350 owners surveyed said they'd "experienced unintended acceleration." And 35 said they'd complained of interference with the all-weather floor mats.

At the time, Toyota did issue a recall of some cars to replace the floor mats, but it denied until very recently that the pedals themselves were at fault. Toyota gas pedals made for it by CTS Corp. of Elkhart, Indiana are now the subject of a 5.3-million-vehicle recall, the company's largest ever U.S. recall.

NHTSA's announcements on the unintended recall issue, have followed Toyota's lead, including a bulletin issued Monday that asked consumers to be on the lookout for pedals that are "harder to depress than normal or slower to return."

Toyota is still firmly denying that electronic interference is a cause of unintended acceleration. "It is not an electronics issue," said Jim Lentz, president of Toyota Motor Sales.