Some safety advocates remain skeptical, but Toyota engineers blasted its cars with electromagnetic waves. The idea is to see if the cars would malfunction and suddenly accelerate.
Toyota says the testing shows the problem is not with the cars' computer system.
"These electronics-the information is hard coded in, and we do all kinds of software testing to understand if there are any software glitches or issues that would affect the quality of the parts. And again through all of that testing, we've found no evidence of that," Kristen Tabar from Toyota said.
"As cars have gotten more complex electronically, we're having more and more random failures in the systems, ranging from brakes, to the throttle, to the steering," Clarence Ditlow from the Center for Auto Safety said.
Ditlow says complaints of unwanted acceleration doubled or tripled after electronic throttles were installed in certain models.