AutoblogGreen

I have the same thing happening to my Chevrolet Cobalt. In my case, I was in the fast lane on a icey road with a semi behind me. Suddenly, I hit an ice patch and my engine totally shuts off. I am slowing down fast with a semi on my tail and I cannot accelerate. About 5 seconds later I get control of my pedals even though the ice patch is way behind me.
Same things happens whenever I hit ice - complete loss of control of the vehicle.

Reply

Sounds like Toyota and in fact all manufacturers need to add a traction control override buttons to future models. Sticky surface conditions require centrifugal force to clean tire treads thus presenting fresh biting surfaces. Think wet snow or mud. Sometimes a little slip is a very good thing.

Reply

Any sort of traction control system will work this way. The concept of the system is to kill engine power if the drive wheels are slipping. That certainly doesn't mean there's a problem with the vehicle in any way, and it's not unsafe for road use. Icy roads are dangerous, regardless of what sort of advances traction control trickery your car has.

Reply

I have never had my traction control disable my vehicle but it that is the case that it is normal then the Cobalt driver above at least gained control seconds later to move from the Semi. It seems like the Prius is just cut off and no control is gained even seconds later. Big difference.

Reply

It seems traction control is going through the problems ABS went. My mother had a Chevy Cavalier and the ABS system would totally lose it sometimes.
It wasn't pretty.

It seems tech is taking control more and more of we want to do. But sometimes we know better then the tech...

Reply

The Cobalt definitely and most likely the Prius have engine-only traction control with no brake intervention. On many less expensive cars they use only engine torque reduction. Without the ability to apply brakes to a single slipping wheel, if you get onto a split-mu surface (one wheel on slippery surface, the other with more grip) the traction control is basically useless if your are on a slope. With brake intervention you can apply brakes to the slipping wheel to transfer the drive torque to the wheel with grip and climb the hill.

The engine only systems can be added to a vehicle with no additional hardware cost aside from some extra memory in the ECU to hold the control code. All the other hardware is already present on the vehicle anyway. For brake control, you need an enhanced hydraulic control unit.

Reply

Obviously Lithous hasn't been in cold weather. My Cobalt will not go up an ice-packed hill unless I push it up there or melt the ice or pick up tremendous speed before hitting ice and coast.
Maybe Mike Magda hasn't been in the cold either.

Reply

"Obviously Lithous hasn't been in cold weather."

Sorry, I'll blame it on global warming (as to why I have not been in severe snow).

Reply

Sam -

> For brake control, you need an enhanced hydraulic control unit.

Yes - but most cars already come with a hydraulic control unit: An ABS pump. It's a slightly different application, but most of the changes are software.

My '95 Ford Contour's traction control system can both cut back the throttle and selectively apply brakes. It's a lot of fun in both the rain and snow: Point the wheel where you want to go and hit the gas; the computer figures out the details.

In any case, traction control shouldn't *kill* the engine.

And remember that it's actually fairly rare to run into significant stretches of *perfect* ice on the road (and I grew up with Ohio winters and rear wheel drive). Everything from paving imperfections to grit at the edge of the road come into play - but I still need torque to do anything with them. I once watched a 4WD truck slide sideways across an icy Pennsylvania bride, all four wheels spinning uselessly (ego forced him to continue, grinding fenders against the concrete railing edge to complete the crossing). A few minutes later, we drove across the same bridge - slowly, on the shoulder - without incident in an FWD econocar. In spite of almost ice-rink conditions in the middle of the bridge, there was plenty of traction on the shoulder.

Reply

I have taken my Prius through 3 Colorado winters, with plenty of driving in all kinds of snow/ice.
It does better than my old Acura Integra did.
and the traction control is a GOOD thing in most snowy situations. Plus, it keeps you from spinning your wheels and making ice right under your tire.

In the case above, just let off the brake, and use the accelerator VERY gently. If that doesn't work, use some sand/gravel/kitty litter (which everyone should have in their car in the winter anyway - it really works). Or get out and push - just like with any other car.

Like people pointed out above, plenty of other cars have traction control (yet some people will use this as anti-hybrid propoganda).

Reply

This definately sounds like a case for the car needing an override button. It makes a lot of sense, that in certain specific situations turning off the traction control is the best option. My '04 BMW Z4 has an override button, and they owners manual gives you specific situations where you should use it.

Reply

Sorry Mike but this isn't the first time you target Toyota. First you say that it makes the least safe cars at http://www.autobloggreen.com/2006/12/19/gas-mizers-flunk-crash-tests/ (specifically Yaris and Scion) Meanwhile many other more expensive cars get poor side crash rating such as Ford Escape. As for "overall" crash test rating the Yaris and Scion do average.

Seems you are specifically targeting Toyota.
Another website saw the information differently
http://blogs.cars.com/kickingtires/2006/12/subcompact_cras.html
"The Yaris without optional side airbags — a $650 option — received the worst side impact rating of poor". Note that it specifies side impact only - yours didn't.
Non-toyota articles though are top-notch.

Reply

I agree. I drive a Prius and the power is cut of completely for a second or two when I accelerate too hard in snow or wet roads. Thankfully, I have never gotten stuck in a snowbank, or on a hill. I wish there was an override button. How hard would that be?

Reply

This is another example of the intrusion of technology into driver ability. I agree that the newer systems help drivers in many instances, but at the expense of the driver to control the vehicle in others. This, along with other problems WILL cause some people to get into accidents. The great majority of people will benefit, and avoid accidents that they would have been in otherwise. The problem with all such systems is that they cannot differentiate between less/more skilled drivers. This is why the "off" button is needed for all systems, including Anti-lock brakes and traction control. Of course, a debate will ensue that the emergency situation cannot be effectivly anticipated by the driver, an therefor there should be no choice. Ahhhh, I love this country, and it's determination to protect me from myself at all costs.

Reply

Phil L

First as background, I've been developing control software for slip control systems (ABS, TC, ESC) for 16 years for a major supplier. An ABS hydraulic control unit is not sufficient. The ABS HCU can isolate the wheel brakes from the drive and modulate the pressure at the wheels but can't apply pressure independent of the driver. In order to do that you need some extra control valves in the hcu to allow the pump to draw brake fluid from the resevoir and then hold the pressure when the driver isn't braking. That adds cost, complexity, noise and wear on the driven wheel brakes. With modern systems, the cost differential isn't much, maybe $10-15 in hardware. But the development effort for a brake intervention system also adds a lot. If not done well, brake intervention can also be pretty rough and uncomfortable. When you consider the small to negative margins on many small cars, any extra cost is generally considered too much and the car-makers will opt for engine only TC.

On the Prius which is probably running in battery only mode during a launch such as described, it may just be a case of cutting the torque too much, and a brake and engine system would definitely help. Even so TC software whould never cut the torque to zero. If this is in fact the case, then Toyota and their ABS/TC supplier does need to go back and recalibrate the system to ensure, this doesn't happen. On the other hand, I'm not sure if the Prius has an inclinometer or g-switch to detect when the vehicle is on a slope. If this is the case, they may have done this on purpose. In a real world situation, when roads typically have a crown (sloping off toward the shoulder) allowing even a small amount of torque on slippery hill, will cause the vehicle to slide sideways over to the ditch, which may leave you stranded even worse. Again, in this case, brake intervention would help avoid this, although if both drive wheels were on a slippery surface even that might not help.

I think all tc systems should have a disable switch as many do, because there are definitely situations where TC can hurt more than it helps, such as fresh deep snow. In this case cutting the engine torque just as you start to move can cause the wheels to fall back and dig in deeper. In this case the option to turn off TC can help you get going. Similarly a split-mu launch on a hill with an engine only system would be easier with the system off.

Having said all that Toyota's statement about an 8-10 degree slope being steep is absolutely right. Eight degrees equates to 17.7 percent slope. Eight degrees may not seem like much, but if you sit at the bottom or top of an 18% hill you'll realize just how steep it is.

Henry

Give Mike a break, he wasn't bashing Toyota, just reporting the facts. The fact is the Yaris did poorly in the side impact crash tests and the Prius seems to have a TC control issue with split mu launches on hills.

Reply

Sam,
Toyota Prius definitely has a deficiency with the Traction control's performance. But so do most models on the market.
Toyota Yaris and Scion did poorly on side impact crash tests when they don't have side airbags installed. But so does the new Dodge Caravan, Ford five hundred, Ford Crown Victoria and many more. Meanwhile all Cadillacs cause serious damage in a rear crash yet there is no mention of this in the article.
I find these specific articles biased.

Reply

Sam -

Thanks for the extra input.

Reply

My 350z track edition has the VDC option installed. Recently trying to go up the driving the VDC made it impossible to just get up the driveway. The throttle was cut so severally that the car crept up the driveway at about 1cm/sec. I quickly turned off the stability control and peeled out up in the garage in a jiffy.

Reply

"Toyota Yaris and Scion did poorly on side impact crash tests when they don't have side airbags installed."

The xB doesn't offer side air bags at all! The Yaris does, but mostly in theory. If you have ever shopped for a Toyota with safety in mind you'll know what I mean. I just had a look at a regional Toyota site, and out of 243 Yaris only 12 had the optional side airbags. I'm sure everyone of those cars will be sold, and 95% of them will not have side airbags. Toyota can afford to match VW and Honda and make safety features standard across the board, but so far the choose not to!

Reply