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Discussion Starter #1
Hi All - can't find this problem talked about anywhere and the dealer doesn't have a clue (he says) so I thought I'd ask about it in a new thread. This is a 2004 Prius, about 2 and a half weeks new, and the one problem I've found with it is one of those intermittent kind that can drive one totally nuts - in the cruise control.

On flats and small hills, the cruise does just fine (give or take a mile per hour or two from what it's set at), BUT - give it a moderate hill, or one presenting enough of a "challenge" that it *seems to think* it needs to "down shift" to maintain speed, the thing will literally seem to do that and begin to surge - as in keep giving it GO and GO and GO, increasing speed up the hill until I either get scared and touch the brake or clear out turn the cruise control off... When that happens, too - and one would think that clearing the top of the hill and the need to "govern" the speed going down said hill to maintain the designated MPH *should* kick in instead, it doesn't - just continues to gain power and speed until I disengage the cruise by touching the brake.

I watched the power display during these times to see if there might be a correlation to the shift between or the interplay between the gas-assist and battery situation -- never did discern any sort of pattern there and the onset or any part of the surging, either up over or down the hill... (there could conceivably be one, but I couldn't tell by looking). After the fifth episode of this type, I didn't trust it anymore and kept it off.

The service guy and the Prius repair guy there both said it was the first they'd heard of it - and that there was no "campaign" about it in the computers.... at least so far. SO - at this point, all agree it's a problem and a "safety one" at that, and that in light of lack of info on it we'll "monitor the situation" for a week or two -- and on the next trip we have planned this coming week where there will be lots of opportunities to test it again.... which seems all we CAN do at this point... but, but but... :shock: :?

QUESTION for y'all then: anybody have any ideas on this? Or prior experience along these lines or suggestions for dealing with it? And might anybody know if the cruise control system on the Prius is a unique creature too or might it be the same kind of critter that is on other Toyotas for the most part??? I've loved the cruise control on our Camry - never had a problem with it ever at all, even on the steepest of hills and going either up or down them, it continues to "govern" just great... so this one was a real surprise and a tad bit scary.

Thanks in advance! And all best wishes - Jan
 

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So the repair guy experienced this same uncontrolled speed up and he says its ok for you to go out and experiment with it? That's nuts.
You should not be engaging cruise control.
You probably shouldn't even be driving the car.
 

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Discussion Starter #3
jsp said:
...

The service guy and the Prius repair guy there both said it was the first they'd heard of it - and that there was no "campaign" about it in the computers.... at least so far. ...
Hi RSnyder - I'm guessing you might have missed this line -- because no - the service folks had NOT experienced this in the Prius, at least... which is why I was writing to y'all. :lol:

That being the only problem, I don't think general driving is a problem, nor has it been. At least, so far. Still - I'm hoping someone "out there" might have some specific ideas for sorting this mystery out! Thanks for taking the time to reply though! -- All the best, Jan
 

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Interesting situation. The Prius uses throttle-by-wire, meaning there is no throttle cable. Many other vehicles operate the same way. Assuming all you have reported is accurate, there appears to be two possibilities:

1) There is a problem with the electronic throttle actuator, not allowing it to be properly controlled by the cruise control electronics, which I believe are built into the powertrain control module, or a problem with the electronics themselves.

2) There is a problem with one of the vehicle speed sensors, or the computer which calculates it, resulting in an inaccurate speed being fed to the powertrain conrol electronics.

If you are having no problems controlling your vehicle speed when cruise control is off, you should be able to safely drive the vehicle. However, the "wait and see" approach of the dealer is, in my opinion, unacceptable. They are paid to diagnose and repair problems. I would tell them to get busy and do their job.
 

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Having thought about this a bit more, it occured to me that this could be a problem with the cruise control switch. The switch has two wires leading to it. Pushing it in various directions or pushing the button connects 4 different value resistors between the two wires. So it seems like if there's a dirty short between the two wires that intermittently looks like the resistance for increase speed by 1 MPH, and if this short was triggered by vibration from the engine when it's running hard, you could see this sort of behavior.

Maybe your service tech can measure the resistance between the two wires while vibrating the steering wheel?

Anyway, sorry for the misinterpretation. I thought you meant this was the first time they experienced it, especially since you said they agreed it's a problem.

Also, if you are going to continue driving, don't turn on the cruise control. If my speculation pans out, you might not be able to cancel the cruise while it's accidentally shorted to a different resistance. Then you could have uncontrolled acceleration (though I guess the brake pedal should still cancel it in this case).

Good luck getting this cleared up quickly.
 

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Discussion Starter #6
UPDATE -- (you guys are great!!!) Just got the car back.

I printed out your ideas and took them with me to the dealer today, and called to follow up with RSnyders thoughts too, soon as I found them. I got to talk with the tech doing the work, on the spot, and he checked out what you suggested (as far as I could tell). No shorts (that was brilliant, by the way) - and no codes of course... and he did several other tests i don't know what to call - in the end we couldn't find anything amiss - BUT I do feel we got as good an exam as we could get. Today it acted perfectly (Murphy's Law in spades!) though we don't have any hills of note here (not like in the north part of the state). Since all they could check out, checked out as OK at this point, I'm a bit more confident and less scared about it... but -- also appropriately cautious! Have another trip planned to the north next week and will see how it goes.

It might well be that it's my own expectations that are out of line -- I have been basing it on prior experience with cruise control on our Camry which continues to be unfazed by hills and climbs of ANY sort, up or down -- a true joy to drive! AND - There's actually a paragraph in the Prius Owners Manual that specifically states not to use the cruise on steep hills, so there probably is a limit to what this specific type of mechanism can handle, thus my experience might just be a factor of this particular technology.

Anyway -many many thanks for your help! May you be blessed likewise! I promise to update with anything more i learn in this regard in hopes it helps someone else. All the best - jan

:D
 

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The stalk control suggestion is a really good one. If you experience the problem again, try an experiment if you have some distance in front of you. As I understand it, you are experiencing a run-away situation, as if the cruise is stuck in 'accel." If this happens again, rather than cancel the cruise or powering it off, try the tap down feature. This will allow for that contact to be made and should result in a return to the original set speed minus 1 MPH. If that happens, you have confirmed it is the stalk control. If nothing changes, we have some more pondering to do.

On the MPG screen, you should see MPG of 100 during the downhill portion. Monitor that screen when you try cruise again. If you are in accel mode, MPG should be something less than 25, confirming high throttle position.
 

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I had a runaway cruise control with a turbo-diesel Dodge/Cummins pickup. It was not a fun experience. The truck went to max throttle/acceleration in traffic on the freeway. The steering wheel mounted switch would not turn the cruise off.

Stepping on the brake would not turn the cruise off!!!

Coast and other controls on the cruise were ineffective. Worse yet stepping on the brake could not significantly prevent the truck from maintaining/gaining speed as the engine was more powerful than the brakes and even with the big diske up front they eventually fade.

I had no reasonable option but to turn the key off and suffer the loss of power steering and power brakes. I managed to get across 3 lanes of traffic and make an off ramp while coasting and got stopped at the end of the ramp. I started the truck with my foot on the brake, intending to turn it off again if it took off out of control but the problem was gone and never happened again.

I have had other problems with that truck's cruise gaining speed over time. Set it for 70 and over time it would creep up to 80-85 but could be reset slower or turned off. When reingaged it would "creep" up in speed again. That was fixed underwarranty. No one had a clue about my total out of control runaway problem. Gee... can't reproduce it reliably... then it must be your imagination...

Do be careful! Be prepared to take emergency action...whatever that is!

Will the Prius allow you to shut it down while driving down the road? If you have to be stopped in park then a runaway cruise could be very interesting.

:D Pat :D
 

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This is so interesting. I've - irrationally, I admit - never trusted cruise control on any car. Maybe I'm just a control freak, but I don't like driving with it and even though I never even heard of any malfunctions, I've never trusted that it would disengage properly. This is absolutely the very first time I've ever heard of it malfunctioning!

I'm not any kind of neurologist or psychologist but I've always had a theory that the more of your body is involved in doing anything, the more completely your mind is engaged it that task. So it was tough for me to give up my manual shift autos, even for the Prius, which I truly love. I wonder if this explains the lapses in concentration we find with hand-held cell phones while driving, BTW. Anyway, do you ever feel your mind wandering once your foot is off the accelerator? Do you feel that if your foot is off the pedal that the extra time required to get it back there could be critical in an emergency? The few times I've used cruise I find I hold my foot above the pedal and rather than having a relaxing experience driving, I'm more tense because of the effort to hold up my foot! I just feel I have far more control without cruise than with it.

My 2 cents. YMMV.

Susan
 

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Susan5s said:
I just feel I have far more control without cruise than with it.

My 2 cents. YMMV.

Susan
Susan, This isn't just a feeling it is a fact, you do have more control doing it yourself rather that using cruise. If cruise control is used properly it isn't a problem and the benefits easily outweigh any downside. Unfortunately many drivers do NOT use cruise control appropriately. That is why advances in cruise are being made to include rate of closure sensors and computers to automatically maintain a safe following distance, with braking as needed. They are incorporating collision avoidance technology.

Improper application of cruise control includes while driving in congested traffic and or in high speed formation. There are fewer opportunities to use cruise safely than most drivers realize. Driving with your foot poised is stressfull. A good question is: poised over which pedal? The brake would be safer to "guard" than the accelerator. The reaction time to get your resting foot on the brake is not significantly different from that when poised over the accelerator. Having your foot "poised" over a pedal predisposes you (see also gestalt psychology) to press THAT pedal whether or not it is the correct one if an emergency arrises.

Have you seen the reports of people driving from the parking lot into a shop at a shopping enter? A distraction sets them up, they note they need an emergency stop and shove their foot down, unfortunately while it is on the gas not the brake and not getting the desired effect they push the control down harder.

Susan, if you are using cruise where it is safe to do so there is no benefit to tiring your leg, poising it for action. Relax and enjoy your Uberwagon.

:D Pat :D
 

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Cruise Control and Sudden Acceleration

I invite you all to view my page on Sudden Acceleration and Cruise Control at this huge ugly web address:

http://home.comcast.net/~Nessim1/Sudden ... otMyth.htm

Early in this thread, someone mentioned that the Prius does not use a throttle cable, but rather a wire. This MAY make my information not apply to the Prius, but on the other hand I don't know how the difference between a "wire" and a "cable" would make a real difference... Either way, if you are interested by the issues of sudden acceleration and cruise control, you should see my page for an explanation and a collection of further info links.

I'm amused at how quickly the "wrong pedal theory" reared its head in this discussion. Read my page to understand why I'm chuckling.

And sheesh stop driving that thing until you get this resolved. Or up your life insurance. Your call. :) --Nessim
 

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Re: Cruise Control and Sudden Acceleration

Nessim said:
on the other hand I don't know how the difference between a "wire" and a "cable" would make a real difference...

I'm amused at how quickly the "wrong pedal theory" reared its head in this discussion. Read my page to understand why I'm chuckling.
--Nessim
What was trying to be said in wire vs cable was that the some cars have mechanical linkages to control the throttle while the Prius is electronic, i.e. throtle by wire, electronic signal down a wire not a mechanical movement of the wire, GET IT?

Don't be too amused by the "WRONG PEDAL THEORY" as it has been proven to be at fault in several NON-CRUISE CONTROL related crashes where someone presses the wrong pedal and not getting the desired result presses it harder, i.e. the gas instead of the brake.

Similar and quite amusing if you can laugh at yourself is the gestault psychology self demo thingy where you are stopped on an incline with your foot on the brake to avoid rolliing backward into the car behind you when suddenly you perceive yourself begining to roll backward. You press down harder on the brake but it doesn't help so you press down REALLY HARD but it still doesn't help! Then you realize the lanes of traffic on either side of you have begun to pull forward giving you the illusion of rolling backward.

:D Pat :D
 

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Re: Cruise Control and Sudden Acceleration

patrickg said:
What was trying to be said in wire vs cable was that the some cars have mechanical linkages to control the throttle while the Prius is electronic, i.e. throtle by wire, electronic signal down a wire not a mechanical movement of the wire, GET IT?

Don't be too amused by the "WRONG PEDAL THEORY" as it has been proven to be at fault in several NON-CRUISE CONTROL related crashes where someone presses the wrong pedal and not getting the desired result presses it harder, i.e. the gas instead of the brake.

Similar and quite amusing if you can laugh at yourself is the gestault psychology self demo thingy where you are stopped on an incline with your foot on the brake to avoid rolliing backward into the car behind you when suddenly you perceive yourself begining to roll backward. You press down harder on the brake but it doesn't help so you press down REALLY HARD but it still doesn't help! Then you realize the lanes of traffic on either side of you have begun to pull forward giving you the illusion of rolling backward.

:D Pat :D
Wow, two Patrick's on the Prius forum from Oklahoma... what are the odds? :D

Patrick
 

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Re: Cruise Control and Sudden Acceleration

Patman36 said:
patrickg said:
Wow, two Patrick's on the Prius forum from Oklahoma... what are the odds? :D

Patrick
Exactly 100%

We picked up our Prius July 3 with 2 miles and a lot of finger prints and some drool on it.

A tad over 300 now while indicating half a tank and computer says we averaged 45.3MPG so far. Hope it gets better as it breaks in a bit. Love the nav systems female voice. I programmed in a destination for the 4th of July but deviated to go to Wally World and she said U-turn in 1/2 mile. Nicer to me than my wife when correcting me.

ON the History Chan program, "Tactical to Practical" tonight they did a bit on autonomous vehicles. They showed a clip of a Prius parallel parking itself as the driver sat there and watched. I was told that the Japanese verson does that as well as has rear disks.

:D Pat :D
 

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Re: Cruise Control and Sudden Acceleration

patrickg said:
ON the History Chan program, "Tactical to Practical" tonight they did a bit on autonomous vehicles. They showed a clip of a Prius parallel parking itself as the driver sat there and watched. I was told that the Japanese verson does that as well as has rear disks.

:D Pat :D
WHAAAAA I wish I would have seen that
oh wait it is on again at 10:00 mountain YAAA
 

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Stepping on the brake would not turn the cruise off!!!

Patrickg said:
Stepping on the brake would not turn the cruise off!!!
This is a shock to me. I thought tab on brake would disengage the cruise control.

Patrickg said:
I had no reasonable option but to turn the key off and suffer the loss of power steering and power brakes.
I wouldn't think this is a reasonable option. Why didn't you slip the transmission into neutral ?.
This would disengage the transmision from the engine while allow you steering power, brake power ?.
Turn off the engine at high speed to me is a really really dangerous move because of lost steering power and the potential of steering wheel lock. I just can't imagine what would happen if the steering wheel lockup while the truck barrel down the freeway in traffic.

Then again I wasn't the guy behind the wheel with white knucle on the steering wheel while his truck barrel down the road at "oh shi*..."speed .....screaming "disengage...disengage... dame it" :shock:
 

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Re: Cruise Control and Sudden Acceleration

patrickg said:
ON the History Chan program, "Tactical to Practical" tonight they did a bit on autonomous vehicles. They showed a clip of a Prius parallel parking itself as the driver sat there and watched. I was told that the Japanese verson does that as well as has rear disks.

:D Pat :D
When you said clip you were not kidding
About a 13 second clip
Looks like the driver selected where to park and then the car parks itself
kinda cool to see the steering wheel turn by itself

Wish the history channel wouldn't get upset with me posting it
Hmmm wonder if someone from japan would record a original?
 

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Knguyen said:
I wouldn't think this is a reasonable option. Why didn't you slip the transmission into neutral ?.
Hmm, engine at full throttle, transmission in neutral ... sounds like a recipe for a thrown rod to me.

I wonder, can you over rev a diesel?
 

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RSnyder said:
Hmm, engine at full throttle, transmission in neutral ... sounds like a recipe for a thrown rod to me.

I wonder, can you over rev a diesel?
isn't there a thingy call "engine RPM limiter ?". I don't get it. How can you over rev the engine in an automatic at full throttle?. I would think that it is safe to blow an engine than risk a steering wheel lock up and crash into some on the freeway at full throttle because you couldn't turn the wheel. I am assuming that when you turn off the ingnition, you may to turn it too far off and lock the steering wheel and discover that the steering lock up at a critical time and then try to turn it but too late. You got 1,2 ,3 seconds before the truck hit something. That the scenarios I am imaging; But apparently it didn't happen.

So what happen when the engine at full throttle?. It run at maxi rpm speed right? Isn't it design to run up to maxi rpm ?
 

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Discussion Starter #20
WELL --- it's not exactly a logical follow up to the above few posts, but I wanted to share an UPDATE with y'all about this cruise-control question that started all this (very interesting stuff - I hasten to add!)!

Took the Prius on another trip through Northern California and southern Oregon last week, going over *some* of the same turf we'd traveled earlier and where I first encountered the CC behavior that scared me... I am aware this might sound silly, but I know no other way to think about it: the dang thing appears to actually "learn"! Actually - it may be more appropriate to think in terms of us/me and the car mutually learning how to drive together... still, I would swear this thing is actively, interactively, learning! (We decided to name the car "Data" - LOL!)

OK - here's the gist of it: on the steeper hills, either up or down, it did seem to be too much for the cruise to handle -- just like it cautions about in the manual. BUT - *this time* on the very same hills that it tried to "run away" on the previous time, THIS TIME it handled them absolutely fine - both up and down! I'm not kidding. The very same hills - approximately the same traffic and weather conditions - and this time the cruise control did just fine; the "tap" down or up one mile per hour suggestion worked fine; it maintained steady speed as directed.

The big test was taking it to Crater Lake, OR -- talk about a long hill, some parts unrelentingly steep... and watching the battery bars go down to the last couple while at the same time seeing there was still a long uphill left to go was a bit unnerving. I kept hearing the words of advice to "*cruise it* on up the hills - don't *power drive* up them like you might in a gas car --- Drive it like a Prius!" repeating in my mind, like a broken record... but it worked - on Crater Lake and several other long steep hills too. By taking it slow and pulling to the side a couple times to let the ICE charge it up a bit when it got really low, before going on further, did the trick. We got to the top just fine and the ride back down again was really fun -- topped off the green bars more than once by the time we were home again!

Still - I think the cautions in many of the above posts are well worth keeping in mind - muchly appreciated. ...Always good to have a notion in the noggin to grab for should the need arise...(knock on wood!). :lol:
 
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