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12v Battery and MFD in 2004 Prius

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by abrown1411, Nov 28, 2008.

  1. abrown1411

    abrown1411 New Member

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    Our 2004 Prius has only around 25K on it, with no extended warranty. We have had it since April 2004. Daughter has had the car at school this year, driving it infrequently in the past couple of months.

    She accidentally left the dome light on for a couple of days last week. Tried to start it, unsuccessful, got dashboard "fireworks" and key would not come out. Waited a bit and was able to get the key out. Left it for 30 minutes or so, and tried to start it again and was successful. Has not seen the same problem and has driven it 200 miles home without incident.

    Fast forward a couple of days... the MFD starts to go out intermittently - unresponsive on energy screens, climate and audio when first starting up, but then will show correctly later. I've read the threads on the 2004 MFD malfunctions, and have seen some of those symptoms.

    Here's my question (in advance of a trip to Toyota service tomorrow): do you think
    (a) the 12v battery is probably dying?
    (b) if you answer yes to (a), do you think the MFD malfunction could be related to that?

    Any insights would be appreciated.
     
    #1 abrown1411, Nov 28, 2008
  2. efusco

    efusco Moderator Emeritus
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    a)If you're on the original 12v it may be dying, but it's not related to the MFD issue. The battery is due for replacement and since it was nearly depleted once it's probably worth the peace of mind to just replace it.

    b)see above. The MFD issues are their own thing. If you're still under warrant get it replaced. If not you've got choices. 1) Fix it yourself. 2) Take it to someone to fix, 3) pay the dealer for a refurb. or new replacement, 4) Buy a salvage and put it in yourself.
     
    #2 efusco, Nov 28, 2008
  3. abrown1411

    abrown1411 New Member

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    Thanks for pointing to that "fix it yourself" link. There's no way I could do that myself, but it was interesting to read what the problem and fix is.

    I wonder, though, whether there are other problems that cause similar symptoms in the MFD (other than what was listed on the TSB.) I was struck by the coincidence of having the low battery and then this problem surfacing when we have had no problems with anything up to this point, had only dealer service, and have only 25,000 miles on it. Wishful thinking I guess.
     
    #3 abrown1411, Nov 28, 2008
  4. rumpledoll

    rumpledoll Member

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    Most likely your 12V battery is dying and needs to be replaced. Lead acid batteries used by the auto industry like the one in the Prius, do not do well when deeply discharged. There are "deep cycle" lead acid batteries that are designed to do this but even they have much shorter lives when drained near capacity.

    When a lead acid battery discharges, both the + and - plates are slowly converted to lead sulfate. Lead sulfate is mechanically less robust than either the lead or lead dioxide that the plate were made of in it's charged state and can and will flake off and gather in the bottom of the battery. This can short out cells if deep enough, and the loss in material reduces the capacity of the battery permanently.

    Additionally and more commonly, when a lead acid battery is left in a reduced charge state for a period of time, the battery becomes more "sulfated" in which the lead sulfate becomes less and less reversible during charging. This is why the advice is given not to leave a lead acid battery in a discharged state.

    Bottom line is that you will need to have the battery replaced.

    Rumple





     
    #4 rumpledoll, Nov 29, 2008
  5. patsparks

    patsparks An Aussie perspective

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    Replace the battery for the peace of mind and it is near the end of its life anyway at 4 to 5 years old so it will be money well spent.

    The MFD wont leave you stranded but it does affect the radio so leave it till later if you like and see if it comes good with the battery replacement. (I doubt it will.) If it keeps playing up go the fix the MFD route. I had mine repaired for $25 after I took it out and apart, if you don't feel you can do the remove and dismantle have a mechanic take it out then a radio tech fix it using printouts of the MFD fix thread instructions. You will save a packet over refurbished or salvage. My repair is over 12 months old and going strong.
     
    #5 patsparks, Nov 29, 2008
  6. abrown1411

    abrown1411 New Member

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    Thanks for the helpful and informative replies. The car is at the dealership right now, waiting to hear what they are going to say. I'm definitely having the battery replaced in any case.

    If it is possible for a radio tech to repair the MFD (as shown in the fix-it instructions), why the heck doesn't Toyota just have their repairman fix it instead of pushing replacement with new or refurbished units and risk alienating loyal* customers for whom it is out of warranty??

    *I bought two Priuses and do all their service at this dealership.
     
    #6 abrown1411, Nov 29, 2008
  7. efusco

    efusco Moderator Emeritus
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    I have to say that the refurb replacements are nice to have...they allow you to switch b/w Energy & Consumption screen by using the INFO button on the steering wheel (if you have that) instead of having to always use the touch screen to do that.
     
    #7 efusco, Nov 29, 2008
  8. abrown1411

    abrown1411 New Member

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    Just to update on the resolution of the problem. It turns out that the 12v battery is still fine (this after 26,000 miles and 4.5 years).

    However.... the MFD is definitely failing. After some dithering, the dealership agreed to replace it for 1/3 of the cost (which comes to around $320); the rest is picked up by the dealership and Toyota. I guess I can live with that.
     
    #8 abrown1411, Dec 22, 2008
  9. eprupis

    eprupis New Member

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    I have 1 2004 Prius with 64000 miles. Except for a MFD replacement under warranty, the car has been flawless, and I note no 12 volt battery issues. Given age and mileage, should I simply replace the 12 volt now, have it checked at the next service and see, or wait til I note any issues with it?
     
    #9 eprupis, Dec 22, 2008
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    How inconvenienced would you be if the car failed without notice? If this is not a big deal then don't worry about replacing the battery now since you don't note any symptoms.

    If you want your car to be maintained at the highest possible state then you may want to replace the battery as a preventive move.
     
    #10 Patrick Wong, Dec 22, 2008
  11. efusco

    efusco Moderator Emeritus
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    Your time on the current 12v is probably pretty limited...but who knows, depending upon your usage habits it may be good for another year...it's hard to say.

    You'll have to replace it at some point. If you expect to keep the car more than another 5 years and want to keep expenses to a minimum then it makes sense to wait until there are signs of failure. If you think you'll replace it in less than 5 years then you might as well replace it now and eliminate the chance of unexpected failure.

    If you choose to keep it until you experience symptoms of failure (and there are often symptoms before overt failure) then I'd recommend keeping one of those jump-start battery packs with you in the car so you can give yourself a quick jump if it should die....be sure to brush up on how to do that in the Prius as you jump at the fuse box under the hood, not at the battery in the back.
     
    #11 efusco, Dec 22, 2008
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