Cruise Control Switches to Runaway Mode

Ummm, the whole thing is, removing one's foot from the accelerator and stomping on the brake WHILE THE FLOORMAT IS HOLDING DOWN THE ACCELERATOR will produce results exactly like what happened here.

No computer special effects required...

 

Confirmed. There is a bypass in the master cylinder to allow the brakes to operate even if there is a full system failure.

It's certainly possible for any car to have a cruise control failure. What makes it more unlikely on a Prius is that it's a drive by wire car and (correct me if I'm wrong) the cruise control is integrated into the software. There are no seperate mechanical components to stick or fail other than the normal throttle body and injector parts.

Software may have bugs, but it rairly just breaks, so software problems tend to show up in entire runs of cars, although you may have to combine an unusual number of factors to reproduce the problem. What we are likely looking at here is either pilot error or a component failure (possible intermittent). If it was pilot error we will never find out.

 

I don't blame anyone for being a bit skeptical so I tried two things:

1. Disconnect the HSD system and stop the car. This can be done by pushing the "Power" button while driving and holding it in for 2 seconds. Results, no power brakes or power steering but the brakes and steering still work fine, some extra effort is require of course. After you do this and stop along side the road you can restart the car in the normal manner.

2. Hold the throttle to the floor and stop the car. I tried it from 55 MPH and there is no problem getting stopped safely. You don't even have to push that hard on the brakes. No dramatics at all, the car just stops, it steers fine the brakes work fine.

Test 2 above proves that unless something else is involved the consumeraffairs.com article was just flat wrong. They didn't even bother to try it before they made up the story.

 

Would something as simple as a failed brake light switch cause problems like this (though not as sever as this scare-tactic article claims)? Did this car get the switch replaced under the recall? Was it maladjusted (the brake switch, not the author) or disconnected? This would explain why the CC stayed on despite pressing the brake pedal.

 

The article says he also tried to shut it off with the cruise control lever and tried putting it in neutral:

["I tried to slow the vehicle by pushing the power button, manipulating the cruise control lever, and putting the vehicle in neutral. All attempts were unsuccessful," he told ConsumerAffairs.Com.

Herbert found himself barreling down the road with the cruise control stuck wide open, running approximately 20 miles over the posted speed limit, all the while continuing to accelerate.]

Thats a lot of stuff to break all at once.

 

As an automotive engineer with experience in powertrain controls, brake controls, cruise controls, general automotive electrical, and a host of others, I am quite confident this "story" is pure fantasy. There are several redundant features to ensure things like this can't happen, not to say that it couldn't in some special case. However, we are told that the cruise control malfunctioned (a specific cause stated, not the symptoms) and that the specific independent controls to terminate the cruise control did not function (power and cancel). Then we are told the master power button did not function, the transmission selector did not function, and the dramatic ending of burning electric motor smells. Sorry, I don't buy it. There could have been an electronic throttle failure, but this is highly unlikely. Even so, the power switch and transmission selector would have functioned. It's a great story, intended to take advantage of previously identified issues (notice how they are woven into the story) and create a "runaway car" episode. Note there was no mention of a racing engine prior to powering down. Hmmmm...where did all that go juice come from? Not the electric motor at highway speeds.

We (automotive engineers) are not perfect. We are humans making 100,000+ parts work together, often now using complex software, and in most cases without incident. We use redunant controls and diagnostics to prevent dangerous situations which might result, or at least a reasonable disable of a malfunctioning system. In this "story" nearly everything that can go wrong does, even though many of the systems are independent of each other. We were even provided a somewhat happy ending, a safe consumer who then had to have his vehicle repaired. But then, wait! The evil maker says there was no problem. 300 miles of "top secret" testing and no solution. A conspiracy against the consumer! All of these complex computer-run vehicles must have minds of their own! You should be warned! Don't buy one!

I feel perfectly safe driving my Prius. You should too.

 

I had a 1986 Tercel that came from the factory with a 5 speed manual transmission and cruise control. I seem to remember that when I pushed the clutch in and shifted the cruise control would cancel.

When I traded the car in for another Tercel 7 years later, no one could believed that it actually came from the factory with cruise control.

 

The story is obviously a bunch of BS and I would love to see TOYOTA take them to court on stuff like this. It has however generated some interesting dialog. Here's my two cents worth. Even if the normal braking was not functioning correctly, what about the EMERGENCY BRAKES !!!! They are a simple mechanical (cable connected) system. The ultimate K.I.S.S.

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