It's obviously pile-on-Toyota week. Transportation Secretary Ray LaHood and Toyota PR are trading barely-polite disagreements, and Japan is making Toyota investigate a new Prius braking problem.

Equally bad, on Monday a celebrity came forward to claim he'd experienced sudden acceleration in his new 2010 Toyota Prius while using the cruise control.

Since he's Apple cofounder and Silicon Valley luminary Steve Wozniak, universally known as "Woz," he got attention. Lots of it.

In fact, Toyota asked automotive Website Jalopnik to send Woz the personal number of Toyota president Jim Lentz. (If only all owners got such treatment ....)

But we think we know what's causing Woz's problem. It's not a sudden acceleration issue. It's Toyota's electronic cruise control, which behaves differently than most other carmakers' systems.

Speaking at Discovery Forum 2010, Woz said, "This new model has an accelerator that goes wild, but only under certain conditions of cruise control,"

"And I can repeat it over and over and over again--safely," he continued. "This is software. It's not a bad accelerator pedal. It's very scary, but luckily for me, I can hit the brakes."

Repeating it over and over

And that's what tipped us off. Not only is the 2010 Prius not subject to the accelerator pedal recall, but every report of accelerator behavior has essentially said that it was a random occurence.

Instead, we think Woz didn't understand how Toyota's adaptive cruise system worked. Because we didn't either, when we first tested the car. Neither did an auto-industry friend of ours who asked to remain anonymous. Here's what he wrote [edited slightly for clarity]:

Ohhhhh, this happened to ME!

It's the way the cruise control in their hybrid cars works. I was driving the Lexus HS250h we tested, and I set the laser distance cruise control.

Accelerating in 5-mph increments

In every other car I've driven that has cruise control, when you press "ACCEL", it accelerates your vehicle for as long as you hold the button down. And it stops when you reach the speed you want and let go of the button or paddle.

But not so, this Toyota system. As you hold the button down, a tiny little electronic counter in the gauge cluster is SETTING YOUR SPEED. With each click up or down, it sets it 1 mph faster or slower.

But if you hold it down, it changes to increasing your speed in 5-MPH INCREMENTS. So as you hold it down at 55 mph, thinking you'll let go at 70 mph when you're at the speed you want, the system is in fact rapidly increasing your target speed.

From 70 to 115 mph

By the time you're at 70 mph and you let go of the button, the computer has set your cruise control speed at 115 mph. And it's now rapidly accelerating you to that speed!

I had to have my passenger look in the owners manual while I was driving to see what I was doing wrong. I tried it a couple times before I realized what it was doing. I mentioned this later to [a Toyota executive]. He just quietly nodded, and looked perturbed...

If we had to guess, we suspect Toyota will find that Woz's 2010 Prius works exactly as it's designed to do. It's just that its cruise control is designed to act in a way that's different to most others, and hard to interpret unless you focus on the digital speed indicator.

Tossing the manual in the trash?

If we knew Woz (we don't, except by reputation), we'd ask him whether he read the (thick-ish) manual that came with his new 2010 Toyota Prius.

Of course, early Apple Macintosh afficionados said the only way to find out if software was any good was to rip off the shrink wrap, put the diskettes in the Mac, and toss the manuals in the trash. If you got it to work, it was good.

Unfortunately, modern cars aren't like that. Even uber-green third-generation Toyota Prius hybrids that get 50 mpg.

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