Toyota, dealing with millions of recalls and claims that it has not yet fixed its safety problems, took a bold step Monday to silence critics who blame faulty electronics for runaway cars and trucks.

The troubled automaker brought together a group of experts to refute studies by an Illinois professor who revved Toyota engines simply by short-circuiting the wiring. Toyota's experts say the experiments were done under conditions that would never happen on the road.

The automaker maintained its assertion that simpler mechanical flaws, not electronics, were to blame.

"There isn't a ghost issue out there," Kristen Tabar, an electronics general manager with Toyota's technical center, told a news conference at the company's North American headquarters in Torrance, Calif.

Meeting with reporters, Toyota addressed the work of David W. Gilbert, an automotive technology professor at Southern Illinois University-Carbondale, whose work has been the basis of doubts about Toyota's mechanical fixes.

At least one outside expert said that even if Toyota's criticisms are accurate, the professor's work shows the systems that allow brakes to override stuck gas pedals can be compromised.

Toyota is mounting a public campaign to reassure its drivers about their safety and defending itself against critics who question the fix for 8 million recalled cars and trucks. Regulators have linked 52 deaths to crashes allegedly caused by the accelerator problems.

The company's fix addresses gas pedal parts and floor mats that can cause the accelerator to become stuck in the depressed position. More than 60 Toyota owners who have had their cars repaired have complained the problem has persisted.