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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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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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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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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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