DETROIT — Investigations into whatever is lurking behind Toyota's crisis of quality have put a spotlight on all that can go wrong with auto electronics — the growing number of wires, sensors and computer chips that have profoundly changed the automobile in the past decade.

Though no smoking circuit has been found so far, a picture is emerging that suggests that the automobile industry's technology is racing ahead of quality-control testing and regulators. It's troubling not only for Toyo-ta owners but for drivers of any modern car that's basically a computer on wheels.

Toyota insists that electronics played no role in the unintended acceleration that has sparked its massive recalls.

Lawyers, regulators, engineers and politicians aren't so sure.

The auto industry has been moving at Pentium speed since the late 1990s to replace mechanical cables and other devices with computers to control everything from brakes and throttles to power steering. Automakers say electronics have made vehicles safer, with devices such as air bags and antilock brakes. It's also made cars more fuel efficient, cleaner and, usually, more reliable.

Still, things can go wrong and diagnosing problems is complicated.

Glitches can include buggy software, circuitry that's randomly influenced by electrical interference and shorts caused by microscopic "whiskers" that sprout from solder. Environmental factors — a blast from a heater vent or moisture from the road — might cause a failure. Age also can be a factor.

"You're looking for a needle in a haystack," said Raj Rajkumar, an engineering professor at Carnegie Mellon University in Pittsburgh. "Those are very hard to reproduce. The problem happens and you go back and check and it's not there. The normal tendency is to blame it on the driver and go on."

And that's what Toyota did initially.

Drivers complained their vehicles accelerated out of control — without them stepping on the gas. But the complaints were largely dismissed by Toyota and government regulators, who blamed mechanical problems or drivers stepping on the wrong pedal.

Toyota began replacing mechanical accelerators with electrical ones starting with the Camry in 2002. Since the 2007 model year, all its cars have had the high-tech throttle.

An analysis of complaints by the auto safety research firm Quality Control Systems found that the number of Toyota "speed control" complaints received by the National Highway Traffic Safety Administration has tripled since the electronic throttles were introduced. NHTSA says 34 people have died because of sudden acceleration crashes in Toyo-tas since 2000.

But the issue didn't get much attention from Toyo-ta until an off-duty California Highway Patrol officer and three members of his family were killed when their loaner Lexus sped out of control and crashed into traffic near San Diego. The Aug. 28 crash received widespread news coverage.

Just over a month later, on Oct. 5, the automaker recalled 3.8 million Lexus and Toyota models in the U.S. because of floor mats that it said could affect pedal movement. In January, it recalled 2.3 million because of sticky accelerators. It later added more than a million to the floor mat recall, and said some vehicles fall under both recalls.

So far, more than 8 million vehicles have been recalled worldwide.

But according to a congressional analysis, 70 percent of Toyota speed control complaints involve vehicles not covered by the floor mat or sticky pedal recall.