VSC, (!), Master warning light, and check engine light on after resetting maintenance required light

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by deacondomino, Sep 17, 2019.

  1. deacondomino

    deacondomino New Member

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    Hi all. I'm driving a high mileage (+230,000 miles) 2004 prius. A couple days after its last oil change, I finally got around to attempting to turn off the maintenance required light. I pressed the power button twice with my foot off the brake while holding the ODO button, and as soon as the maintenance required light turned off, the VSC, (!), and master warning light and came on. Tried the same procedure again, and (naturally) they stayed on. Tried reading the codes with an OBD2, got U0100. Tried wiping the codes with it, they immediately returned (or perhaps never left), and now the check engine light has joined them. Any idea what happened, or how to fix it?
    Addtional context: the car has been in the family its whole life, and was behaving well before (and until now, after) the recent oil change.
    Anything helps.
     
  2. PriusCamper

    PriusCamper Senior Member

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    Congrats for keeping such an awesome car in the family for so long... When did you last replace the 12v battery?
     
  3. deacondomino

    deacondomino New Member

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    Thank you! It's been about 4-5 years since we last replaced it, now that I think about it. I probably should have considered that earlier!
     
  4. PriusCamper

    PriusCamper Senior Member

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    Just don't buy an Opitma battery, they resell their defective batteries without testing them and every month we get somebody on here saying: "Replace my 12v and now my car won't start"
     
  5. TMR-JWAP

    TMR-JWAP Senior Member

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    Out of curiosity, did you verify the odometer was actually on odometer and NOT on a trip meter setting prior to doing the reset procedure? That should always be the first step.

    If it was on a trip meter, there's no telling what may have actually reset...……...there's all kinds of secret combos out there

    With my luck, I would have erased all the SKS key info or the main ecus.

    Hopefully it's nothing crazy like that.
     
    #5 TMR-JWAP, Sep 17, 2019
    Last edited: Sep 17, 2019
    PriusCamper likes this.
  6. dolj

    dolj Senior Member

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    And rather than just changing out the 12 V battery willy nilly, it would be an idea to do some tests, or get it tested at a auto-parts store before it is condemned. Unless the battery is dropping under 10.5 V under load, it likely is just a big distraction.
    To get back on track, U0100 = Lost Communication with ECM / PCM "A"
    There are 3 INF codes associated with that code, that will give a bit more information to pinpoint where the problem may lie. You are looking for 211, 212 or 530.

    The battery ECU receives signals from the hybrid vehicle control ECU, ECM, and gateway ECU via CAN (Controller Area Network) communication.

    MONITOR DESCRIPTION
    If the battery ECU detects malfunction in the CAN communication with the ECM or hybrid vehicle control ECU, it illuminates the MIL and sets a DTC.

    MONITOR STRATEGY U0100:
    Column 1 Column 2
    0 Related DTCs U0100: Communication between ECM and battery ECU/Non-received check
    1 Required sensors/components
    • Main: ECM
    • Sub: CAN bus line
    2 Frequency of operation Continuous
    3 Duration 0.68 seconds or more
    4 MIL operation Immediate or 1 driving cycle
    5 Sequence of operation None


    BTW, what is the make/model of your OBD2 reader?
     
    #6 dolj, Sep 18, 2019
    Last edited: Sep 18, 2019
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