MFD doesn't remember settings in 2008 Touring

Discussion in 'Gen 2 Prius Main Forum' started by GTW, May 25, 2018.

  1. GTW

    GTW Junior Member

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    ----USA----
    I just purchased a 2008 Touring. The high voltage battery was reconditioned as a part of the sale, and it comes with a 1 year warranty.

    The issue I am having, is that the MFD doesn't remember any settings. I do press the 'Save; button where I see one. Every day, the screen's brightness is at 'default'. The radio is on, tuned to the lowest frequency on the AM band. All of the buttons work, and the screen is responsive, but it doesn't hold any preferences after the car is powered off.

    I entered the car's self-diagnosis on the regular battery, and it shows 2 values.
    1) Before the engine is started, the diagnostic will show 10.8 V.
    2) After the engine kicks on, the diagnostics show 13.8 volts.

    I use a code reader with Dr. Hybrid to monitor the high voltage battery pack.

    When driving, Dr. Hybrid indicates that the 'pack' voltage averages around 227 volts.

    IS there anything in these readings that might explain why the MFD display doesn't hold preferences between uses? Does the MFD have a small watch-battery backing it up that needs replacement?

    Thanks for looking.
     
  2. dolj

    dolj Senior Member

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    Given the above info, the 12 V aux battery is more than likely requiring replacement. You are loosing the settings because the 12 V bus looses power. A new working and fully charged 12 V battery will sort that out.

    A good source of a reliable 12 V battery is a dealership. Ring around and get the best price you can.
     
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  3. GTW

    GTW Junior Member

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    I've read much about weird indications when the 12V is low, but the car starts okay. This is what threw me for a pause. If the car batt is really under 11volts from a cold measurement, I'd think the vehicle wouldn't start. So far that's been reliable. It seems I'm on a short leash here. Thank you for your reply.
     
  4. Mendel Leisk

    Mendel Leisk Underfoot

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    Check the voltage with a multimeter, with the car off, first thing in the morning. If it's really just under 11 volts, that's a toast battery; a healthy battery would be reading 12.6 or higher.

    upload_2018-5-26_10-8-8.png
     
  5. fotomoto

    fotomoto Senior Member

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    If you're new to hybrids, you may not understand that the 12v doesn't "start" the car but merely brings it on-line. The much stronger 200v hybrid battery crank starts the gasoline engine so you don't get that very slow-crank, "whir-whir", hint like regular cars do when the 12v is very weak.

    IIRC, the ECU's (computers) require 11v minimum to boot. After that, the EV side of the equation (battery, inverter, etc) supplies all the power needed via its dc-dc converter to the 12v systems (hence your healthy 13.8v readings). Losing presets is a classic sign of a weak 12v in any vehicle.
     
  6. GTW

    GTW Junior Member

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    You are correct, I am new to hybrid., This is my 2nd week of ownership, from a Seller who mainly deals in used Prius'. He has 20 or so at any given time, but I didn't give him any time to prepare this car before purchase. It's my own fault, but circumstances pushed the urgency.

    Anyway, in shopping for a replacement battery, a mention was made of the smart key system. I have turned that off for now, every little bit counts until I can get the new batt. Thank you, Fotomoto, Mendel Leisk, & Dolj, for your help. Take care.
     
  7. GTW

    GTW Junior Member

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    I have now replaced the 12-volt battery. I went with the highly recommended Yellow Top battery since it was reported to have been a better than OEM replacement.

    AND NOTHING HAS CHANGED. The MFD still does not remember any user settings. The radio still comes on, the screen settings are still ''Center", Bluetooth does not remember my phone, etc. I'm not sure which direction to look next.
     
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