No simple fix for Toyota's recall problems

The simple-sounding problem that has prompted Toyota's massive recall is far from straightforward in reality.

Experts say the sudden acceleration that can apparently affect some cars is probably not a single issue but a combination of complicated interconnected conditions.

Nothing illustrates that more than the contradictory statements from the two companies involved.

Toyota is telling the government that it thinks a friction problem in its accelerator pedal mechanisms may make the pedal "harder to depress, slower to return, or, in the worst case, mechanically stuck in a partially depressed position."

CTS, the US supplier that makes the devices for Toyota, said that the friction problem accounts for fewer than a dozen cases of stuck accelerators, "and in no instance did the accelerator actually become stuck in a partially depressed condition."

If there were a simple answer, a one-thing gone wrong glitch with a fix, it is unlikely Toyota would be in the mess it is now in.

When Toyota last Autumn recalled 4.2 million vehicles, then added another 1.09 million vehicles yesterday, it said it was because floor mats were interfering with the pedals.

That may have been an issue, but now the company is saying its latest recall of 2.3 million vehicles is linked to worn pedal mechanisms.

External safety experts say possible causes also include the complicated electronic sensors that relay the message from the pedal to the engine, the design and location of the sensor system, a lack of a fail-safe override mechanism, and even a certain media-fed awareness that puts more people on the lookout for the problem.

Academic researchers say the rarity of sudden acceleration problems is a telling sign to the difficulty of determining what's going wrong.

"This is very unusual and happens on a very rare circumstance, and a whole bunch of things have to happen simultaneously," said Raj Rajkumar, head of Carnegie Mellon University's automotive research lab.

Sean Kane, president of Safety Research and Strategies , said he was certain there was no single cause and he has logged thousands of stuck pedal complaints.

"We are convinced that this a multifaceted problem," he said. "You've got a multitude of problems that are coming to the surface that result in one thing: unintended acceleration."

How an accelerator pedal is supposed to operate is anything but complicated. Stepping on the pedal starts a chain of events to open the throttle, sending more petrol and air into the engine. The car goes faster. Stop pressing, the engine's speed decreases and the car slows down.

At first, the pedal was directly linked to the throttle, or hydraulics did the job. Then more than a decade ago, electronics started handling the relay.

Most throttle systems on modern vehicles are electronic. Typically, the driver steps on the accelerator and gets resistance back from a spring. The movement activates components in the pedal assembly that send an electronic signal to the engine-control computer, and a signal from the computer feeds more fuel to the engine.

In documents provided to the government, Toyota indicated the mechanical problem that causes the pedal to stick occurs when water condenses inside the system when the heater is on. The company also thought a material used to make the pedal system was a problem, so it switched to a different material, but the problem persisted.

See also:

http://www.timesofmalta.com/articles/view/20100128/local/toyota-extends-safety-recall-to-europe