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Traction control shuts down engine on slippery surface. (http://www.consumeraffairs.com/news04/2008/01/prius_winter.html)

http://www.cleanmpg.com/photos/data/501/Teddygirl_s_Prius_in_the_snow.jpgJoe Benton - ConsumerAffairs - Jan. 29, 2008

Toyota’s TRAC still an issue? -- Ed.

One year after first reports in ConsumerAffairs.Com that the Toyota Prius traction control system can fail to operate properly on a snowy road, Prius owners report the hybrid’s TRAC system is still inadequate on slippery inclines.

One Vermont Prius driver, suffering through a recent January snowfall, described Toyota Prius traction control as "dangerous in mountainous snow country.”

The Vermonter wrote that the “system is flawed and should definitely be modified. In marginal traction conditions, such as Vermont winters, the Prius traction control system will shut down power to the drive wheels and prevent forward movement.”

In January 2007, ConsumerAffairs.Com reported the traction control failure in the Prius as one of the oddest Prius stories on file.

"When my car is on any kind of slick surface that causes one of the front wheels to slip, all power to the drive system is stopped," wrote Christopher of Reston, Virginia… http://www.consumeraffairs.com/news04/2008/01/prius_winter.html

I have to wholeheartedly agree that the TRAC control in the Prius could be dangerous! I have had more than my share of run-ins with the system in my car. One in particular that I could describe as dangerous would be a time when I nearly got T-boned in the right side because of it. As some of you here know, since I'm a hypermiler, I pay very close attention to traffic and don't do anything that would require sudden acceleration so I plan my movements accordingly. Several weeks back I was turning left at an intersection with the closest oncoming traffic at nearly 1/4 mile away on a road with a 45 mph speed limit. About half way into my turn, one of my front wheels encountered some slush that was maybe a foot or less wide. The car cut all power to the wheels and I nearly came to a stop with traffic getting dangerously close. The only thing that saved me was that I had just enough forward momentum to carry me through. If the slush had been any closer to the beginning of the turn, I would have been toast. My mom was in the front passenger seat and my wife was in the rear right behind her. I may have survived but the two most important women in my life may not have. I think this is definitely a design flaw and Toyota should take the approach of applying a brake to the offending wheel instead of cutting all power. I used to drive my grandpa's tractors on his farm and, when the rear tires would start to lose grip, you could alternately apply brakes to each rear wheel and and get through; unless of course you had done something dumb and got into something up to the axles. If technology like this worked in the '50's on a farm tractor I would think that Toyota could do something similar. Since I already have VSC it should only be a matter of some software to change the TRAC to something better. A person on Priuschat has an FJ(?) Cruiser from Toyota and he reports that it does apply brakes to the slipping wheel so I would think it should be able to be used on the Prius. Sorry for the long-winded reply. Rant mode off.:o

... A person on Priuschat has an FJ(?) Cruiser from Toyota and he reports that it does apply brakes to the slipping wheel so I would think it should be able to be used on the Prius. ...

You are probably referring to Jayman (a local Prius driver in my city). Yes, he's very vocal about the TRAC issues mainly because he has an earlier model Prius II (2004). He solved most of his grievances by using studded tires, but despite that he has quite a collection of episodes to talk about.

In my case, we also had a couple of scares going up our driveway in the winter with Michelin X-ICE tires on (2007 model), but even in those situations we were never out of control and in danger. The car just refused to climb the driveway, that's all.
While I am still not saying the TRAC system is perfect, I would even say that this issue is being blown out of proportions and it seems geared to make the Prius II look bad without much of a big reason - especially for the 2007 models and later models. I suspect the TRAC software updates should also alleviate the problem for the earlier year models.


Cheers;

MSantos

You are probably referring to Jayman (a local Prius driver in my city). Yes, he's very vocal about the TRAC issues mainly because he has an earlier model Prius II (2004). He solved most of his grievances by using studded tires, but despite that he has quite a collection of episodes to talk about.

In my case, we also had a couple of scares going up our driveway in the winter with Michelin X-ICE tires on (2007 model), but even in those situations we were never out of control and in danger. The car just refused to climb the driveway, that's all.
While I am still not saying the TRAC system is perfect, I would even say that this issue is being blown out of proportions and it seems geared to make the Prius II look bad without much of a big reason - especially for the 2007 models and later models. I suspect the TRAC software updates should also alleviate the problem for the earlier year models.


Cheers;

MSantos

Yes, it is Jayman. Since my car is an '07 it either was missed for the upgrade or it wasn't enough. My son's '99 Saturn can run circles around my Prius and it has more power and no traction control plus it's a 5MT.

Is it possible to buy a prius without traction control, or turn it off?

Is it possible to buy a prius without traction control, or turn it off?

Unfortunately, no on both accounts; sort of. You can't by a Prius without TRAC but there is a hack to turn it off. I haven't gotten enough nerve to do that because I can't seem to get a clear answer on how much spinning the MG sets can take before they are damaged. I would think they should be able to handle at least up to the car's top speed but I'm not sure. Hobbit?

I though very seriously (and carefully) about the hack to turn off the TRAC system, but as with many other hacks, these measures are not without side effects and possible consequences. This is because I personally view TRAC as more of a net benefit than a hindrance.
IIRC, it consists of defeating the system with a bit of tape thus interfering with the wheel spin sensor preventing it from triggering the TC.

Cheers;

MSantos

Actually, it has to do with a sequence of gas pedal and brake pedal pushes and the shift lever being moved a certain. way. For obvious reasons I won't say how to do it on the public part of the forum.;) As I mentioned before, I can't bring myself to try it.

so this is something that could be turned on and off doing that hack?

so this is something that could be turned on and off doing that hack?

Yes. The next time the car is powered up from a shutdown it will go back to normal operation.

A car that cuts power to wheels when trying to cross traffic.

That is dangerous.

Keith

A car that cuts power to wheels when trying to cross traffic.

That is dangerous.

Keith

My underwear were nearly a testament to that fact.:eek::D

My grandfather has an '04 Prius and complains about this problem too. I should mention he lives in Duluth, MN -- which is known for not only tons of snow but huge hills too. Very dangerous situation. I can't believe Toyota hasn't fixed this yet.

And why can't we talk about the hack to turn it off in a public forum? There's nothing unsafe about turning off TC; heck, most cars still don't have it. Even Saturns, with their useless attempt at TC, have a dashboard button to disable it. Since when are people incapable of modulating power with their right foot? Honestly, anyone who thinks they need TC shouldn't be driving in snow anyway!

My grandfather has an '04 Prius and complains about this problem too. I should mention he lives in Duluth, MN -- which is known for not only tons of snow but huge hills too. Very dangerous situation. I can't believe Toyota hasn't fixed this yet.

And why can't we talk about the hack to turn it off in a public forum? There's nothing unsafe about turning off TC; heck, most cars still don't have it. Even Saturns, with their useless attempt at TC, have a dashboard button to disable it. Since when are people incapable of modulating power with their right foot? Honestly, anyone who thinks they need TC shouldn't be driving in snow anyway!

In a Prius, turning off the TC could damage the MG sets if the wheels are allowed to spin too fast. I just don't want to discuss something in public;) that someone may misuse and try to hold me responsible for.

I guess you can not just pull a fuse?

I think I'm the only Prius driver on Earth who doesn't have an issue with the traction control. Yes, it backs off power when the wheels start to spin. But WTF good are the wheels going to do you if they're spinning in place? Hold down the gas pedal (to the floor if you want) and the system automatically delivers the most torque that the road surface will allow by backing off and re-applying about once a second. Even in deep-ish snow it just digs its way out gradually. I've had it cut when I scrubbed out while entering a roadway, too, and thought surprising to me, the system put power back immediately.

I think people are just so used to spinning wheels and lots of noise while the front end slides sideways that they think they're being cheated when that doesn't happen. Nevermind that nothing productive is really happening amidst the spinning and noise.

In a Prius, turning off the TC could damage the MG sets if the wheels are allowed to spin too fast. I just don't want to discuss something in public;) that someone may misuse and try to hold me responsible for.

How could spinning wheels damage anything but tires?

Sounds like a design flaw to me. Its not like folks that buy a PII will be power braking them at the local drag strip.

TC should beable to be turned off....

Traction Control is designed for low speed situations, not high speed skids. The problem with the Prius as I read it is in accelerating situations such as Larry described. A spinning tire can still propel a car forward in snow. If I push the "snow" button on my Highlander it defeats the TC and allows the tires to spin. Sometimes it is the only way to get going at a reasonable pace, even though steering is hampered. To me TC is helpful only when trying to accelerate and turn simultaneously. One of the hardest lessons for my kids to grasp was to ask the tires to do only one thing at a time in snow/icy conditions. Brake before the turn, accelerate gently during a right turn after a stop, etc.

I've had several cars that had traction control with ability to override, giving me the ability to accelerate faster in snow.

Keith

I think people are just so used to spinning wheels and lots of noise while the front end slides sideways that they think they're being cheated when that doesn't happen. Nevermind that nothing productive is really happening amidst the spinning and noise.
On occasions, the Prius traction control system is so aggressive in cutting power that it immobilizes the vehicle. I remember reading a bit of what jayman had to say on the issue in his vehicle. At icy intersections, he said that the car could become immobilized by the traction control while other vehicles had no problem getting going.

On occasions, the Prius traction control system is so aggressive in cutting power that it immobilizes the vehicle. I remember reading a bit of what jayman had to say on the issue in his vehicle. At icy intersections, he said that the car could become immobilized by the traction control while other vehicles had no problem getting going.

I agree with you Mike. In those cases. it would be nice to have some spin since it would at least carry you forward rather than leaving you a sitting duck.

Yes, there are many situations where moderate wheelspin is the only way to get -- or keep -- yourself moving. I understand that excessive wheelspin can damage things, but only when excessive. After all, those of us privileged enough to have grown up in states that required Drivers Ed recall the warnings about transmission damage from careless back-and-forth rocking to get unstuck -- but they taught that technique for a reason.

By all accounts the Prius' TC is excessively aggressive and cuts power even at a hint of wheelspin. In very slick conditions you can't help but have some wheelspin. And in deep snow (as well as mud and loose gravel) you actually get better traction by breaking the tires loose. Studies have shown ABS to be very detrimental to stopping distances (by as much as 30-40%) in those conditions, because on loose/deep surfaces you can actually stop much faster by locking up the wheels. [This is not true on solid surfaces like wet or dry pavement, hardpacked dirt, packed snow or ice -- then you're better off with ABS].

There _is_ a problem with the traction control because so many experienced drivers perceive there to be a problem.

The stock Michelin low RR tires on my '04 Solara are useless on certain types of snow. Switching to different tires in the winter solved my problem. If you live where you feel stock all-season tires are not doing the job, consider an alternative set. Wouldn't a few percent loss of FE be worth peace of mind?

I had traction control on my '01 Olds Alero. It had a button on the shifter to defeat it.

my $.02,
cheers,
Bill

You are probably referring to Jayman (a local Prius driver in my city). Yes, he's very vocal about the TRAC issues mainly because he has an earlier model Prius II (2004). He solved most of his grievances by using studded tires, but despite that he has quite a collection of episodes to talk about.

In my case, we also had a couple of scares going up our driveway in the winter with Michelin X-ICE tires on (2007 model), but even in those situations we were never out of control and in danger. The car just refused to climb the driveway, that's all.
While I am still not saying the TRAC system is perfect, I would even say that this issue is being blown out of proportions and it seems geared to make the Prius II look bad without much of a big reason - especially for the 2007 models and later models. I suspect the TRAC software updates should also alleviate the problem for the earlier year models.


Cheers;

MSantos

Is there any difference in the 07 & later models?

Did Toyota upgrade the TRAC system?

I think I'm the only Prius driver on Earth who doesn't have an issue with the traction control.Not the only one. I haven't seen snow in 15 years. The only ice I've seen in that period was in my iced-tea.

How could spinning wheels damage anything but tires?

<Speculation Disclaimer="I'm a software engineer not a mechanical engineer, so may be real off base">
I think it has to do with the PSD (power split device). The hybrid drive train has multiple motors all providing power at the same time. The PSD is used to balance those torques against each other and provide a resultant torque to the wheels. If there is no resistance offered by the wheels the MG's may be unhendered in their power delivery dominating the torque balance of the PSD. One of the MG's jobs is to balance this battle. I could forsee that the engineers would have to set up limiting conditions on these equations to determine how much of a battle condition they could balance. TRAC may have been their answer. Which is also why it may be real hard to fix and real dangerous to disable. If part of TRAC's job is to keep the MG's within their mechanical tolerances, this TRAC system is effectively a mechanical and not as software based. No fuse to pull. You'd have to replace the MGs
</Speculation>

One thing I'd be interested in is how TRAC behaves in Prius models that have either the EV mod or factory EV. If EV is engaged and your only power device is the MG is TRAC less aggressive in cutting power? I just haven't heard this much noise coming out of Europe and England where I would thing TRAC problems would also present issues. If I recall, all EU and British Prius models have factory EV. Maybe Factory EV means more than hooking up pin 27 ;).

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