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Screwed-up TPMS: Tell me how this makes sense

Discussion in 'Gen 2 Prius Technical Discussion' started by brick, Nov 11, 2008.

  1. brick

    brick Active Member

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    We just finished getting the TPMS fixed on Prius #2 after having the tires replaced about a week ago. The symptom was the the light stayed on and could not be reset. The light did NOT flash when we started the car. The dealer says that they didn't break the sensors (as I had suspected) but instead the computer was screwed up. The service writer's explanation was that as soon as the tire lost pressure while they worked on it the TPMS became "confused" and could no longer be reset with the button. And they had to "re-download" something or another to the tune of $50 for diagnostics and $50 for reprogramming. (We are going after the tire shop for reimbursement.)

    1) Does this make sense? It sounds like some programmer was asleep at the wheel when writing that code.

    2) Does this mean that the tech left the car running while he was swapping out the tires?

    3) Do I seriously have to take the car to a Toyota dealer to get new tires without something coming out screwed up?
     
  2. jpadc

    jpadc Type before I think too often

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    I wonder if the problem could have been "fixed" by a forced computer reboot. That is disconnecting the battery and then reconnecting it. I've not searched the site for others' experience with this, but I bet there is some.
     
  3. brick

    brick Active Member

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    In retrospect, I wish I had thought to try that. At the time I was more concerned about preserving any useful information that might have been stored in the systems.
     
  4. morpheusx

    morpheusx Professor Chaos

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    I just had my tires done, bought them from tire rack and had a local independent high volume shop put them on for $50, with no problems. He said they see them several times on a daily basis and that almost all newer cars have them.
     
  5. David Beale

    David Beale Senior Member

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    Had no problems when I threw away the junk OEM tires last fall. That was NOT a Toyota dealer! I'm not crazy. I would NEVER buy tires from one of them. They are ripoff artists!
     
  6. narf

    narf Active Member

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    This seems very wrong. The Toyota service writer claimed that the computer failed because it read no air pressure in the tires? So, every time you get a flat tire you would have to reflash the computer? That's absurd. If they didn't find any sensors damaged by the tire shop then it's not the tire shops fault.

    If the car is under warranty, I'd go back and ask for them to cover it. If they won't, then ask them what the tire dealer did to damage the system. you can always escalate this to the zone office.
     
  7. brick

    brick Active Member

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    Despite having it in writing from Toyota that the tire store could have been the only source of the fault, they have no interest in rectifying the issue. The owner's claim was "It's a new car, we are not responsible for knowing how it works. This would have happened no matter what. It's your responsibility for buying a car with new technology. You are in the minority so we don't care if you ever buy from us again." No matter that **every** new car has or will have TPMS in the very near future.

    But of course that's not part of the technical discussion. I would love to hear from anyone with more knowledge of what might have actually happened. The information I have already posted is all that Toyota has to give me.

    Oh, and anybody in the COLA area looking for new tires feel free to PM me so that I can steer you away from the same headache. Not only has this establishment been unhelpful, but rude on top of it.
     
  8. galaxee

    galaxee mostly benevolent

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    DH is buried in homework but i will try for a technical explanation for you this week or this weekend, brick.
     
  9. brick

    brick Active Member

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    Wohoo!! But I'll understand if he doesn't have time given the homework and all. I remember the days (and nights) of nightmarish homework.
     
  10. galaxee

    galaxee mostly benevolent

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    it's possible the system went haywire. but there is no reflash of the tpms ecu. reprogramming is just re-entering those numbers. something's kinda fishy in that explanation.

    or, the tire place broke one sensor and replaced it without telling you. but then the dealer would have had to break down one tire to get the number off the sensor.
     
  11. john_dough

    john_dough New Member

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    Considering it's minor benefit of letting you know when a tire is 25% low on air (big deal), this TPMS feature has got to be one of the most cost ineffective items on the car--seems like it was put in as an income generator for the dealers/repair shops.
     
  12. brick

    brick Active Member

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    Thanks for the input! The possibility that they covertly replaced a sensor makes sense except that I would have expected the TPMS light to flash upon system start, no? Instead it went solid immediately as if it were functioning and detected a flat.

    The only convoluted explanation I can think of is that the tire shop did break a sensor, paid Toyota to install the part, and somehow convinced the dealer to feed us some bull about reprogramming to get us to pick up that part of the bill. That's a really weak story, though.

    As for the merit of the system, I actually think it's quite valuable. Last year we were driving around in the middle of nowhere when the TPMS light came on due to a nail in the right rear. It gave us just enough time to find a safe place to pull off the road before the tire went completely flat. Another minute later it would have been flat, possibly on the way to blowing out since we were moving at nearly highway speeds. So if nothing else it saved us the cost of replacing that tire, which went another 15-20k. Not to mention the possible damage to the rim.
     
  13. David Beale

    David Beale Senior Member

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    TPMS was not added to generate income for dealers. TPMS was added to cover certain rear ends (govt and tire companies) after the Ford Exploder tire episode. Required because the great unwashed public is dumb. They won't check their tires unless a flashing light tells them to.

    Your tax dollars at work.
     
  14. narf

    narf Active Member

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    If the system doesn't detect the sensors, it ignores them for about 1 hour, then flashes the warning light for a few minutes followed by a solid light. How do I know? That's what happens when I use my winter wheels. I keep my stock wheels in the garage near the car. When I drive more than an hour away the light flaishes. If the car is never on for a full hour at a time the light never goes on.
    If the light immediately went on, I'd think that indicates a malfunction.
     
  15. David Beale

    David Beale Senior Member

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    There is a remote possibility that parking next to another Prius can confuse the system. I know the Mazda RX-8 had this problem. The TPMS sees the other cars sensors and gets confused. The newer TPMS we have with serial numbers on each sensor -should- reduce this possibility but you never know.
    Murphy -WAS- an optimist after all.
     
  16. brick

    brick Active Member

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    That's an interesting thought about the 2 Prius parked together. It hasn't been a problem for over a year and a half, though. And it seems an odd coincidence that it would decide to randomly throw a fit the same day we had new tires installed.

    re: narf, yup. Before heading south I had snow tires and saw the same beavior. This was a problem for a couple of days so it should have found the missing sensor at some point before we got Toyota to do...whatever they did.

    At one point I wondered if swapping all of the sensors around the car confused the system because they were no longer registering where the computer expected to see them. I also thought, maybe this has something to do with the reason we're only supposed to rotate tires on the same side, not across. Maybe? It seems like an awfully silly explanation...almost as silly as the grande conspiracy between the tire shop and the Toyota dealer.
     
  17. misslexi

    misslexi Member

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    I've had my share of run ins with TPMS on my Prius, mostly due to lack of knowledge on the part of tire stores and the dealership front line people. It's not limited to Prius, my better half drives a Lexus with TPMS that malfunctioned around 30K miles, the dealer says it's not that any of the tires are low but that something else is wrong in the system somewhere. So you take it in, they fiddle with it for a day while you drive a loaner, it works for a few weeks then not. Repeat. Now I'll admit our time isn't worth very much, and Lexus does serve Starbucks coffee, but after a while the Seinfeld solution of electrical tape over the light starts to look good.
     
  18. galaxee

    galaxee mostly benevolent

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    that's right, forgot it blinks for a minute before it comes on solid when there's a problem.

    well... no explanation seems to make much sense to explain what's up, but again the tpms ecu doesn't get reflashed in any way. unless they just disconnected the 12v and reconnected it... and didn't want to tell you that.
     
  19. brick

    brick Active Member

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    I guess I wouldn't be surprised if that were the case. I really should have pulled battery negative myself, but was blinded with a conviction that I **knew** (not so much) that it was a bad sensor. Ahh, well. The system remains functional and I no longer have to worry that my fiancee will put herself in a ditch because the tires are shot.
     
  20. brick

    brick Active Member

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    :mad: I spoke too soon!

    She took off at 4AM on a ~900mi road trip to visit our family up north. At 4:30AM my cell goes off a few feet from my head on the night stand. She was worried because the TPMS light had started flashing, then went solid, which I told her was a detected system fault. So now I'm back to square one and won't have access to the car until I join her next week. (15 vacation days per year never seems to cut it.) At least now they might have a real solution since the car actually sees a problem.

    Misslexi, could you please describe the issue with you husband's Lexus? Does the light flash to show a fault or does it just tell him he has a flat tire?