Warning Lights go out after cleaning negative battery terminal??

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by Merv Himself, Feb 10, 2020.

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  1. Merv Himself

    Merv Himself Junior Member

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    Lots of background and then a question at the end. Thank you all for your patience. This has happened twice so far in the past 6 months.

    Upon trying to start the car a wonderful array of warning lights come on. I'm dazzled, yet dismayed:

    Brake System Warning Light
    Check Engine Light (aka malfunction indicator)
    Hyrbid System warning Light
    Slip Indicator Warning Light
    Also, Unable to select between EV/PWR/ECO modes, but I.C.E. is running.

    So then I look at the 12V battery. Negative terminal has a slight crack in it because some schmuck (probably me) was too rough in attaching the connector years ago. But all voltages seem to check out as far as I know:

    At Rest (after sitting over night): 12.86V
    With I.C.E. Running 14.41V
    With ICE not running: 14.45V

    Slight corrosion on the negative terminal, so what the hell, I clean it up real good, then re-attach connector, and VOILA! Warning lights go away and the car runs like a top.

    Next, I check the inverter coolant reservoir. Certainly not a tidal wave in there, but mild ripples which indicate SOMETHING is causing some turbulence. (hopefully the inverter coolant pump) Ripples continue even after the I.C.E. shuts off, so I know it's not just engine vibrations.

    QUESTION: Since voltages seem okay, what could be causing these warning lights? Is my cleaning of the negative terminal just a coincidence? Any suggestions or other things to look for would be greatly appreciated.

    MORE INFO:
    2013 Prius V . 160,000 Miles.
    Optima 12V battery is 3.5 years old.
    Otherwise, car is running fine, avg 49MPG
     
    #1 Merv Himself, Feb 10, 2020
  2. sam spade 2

    sam spade 2 Senior Member

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    Maybe.
    You are missing the most important voltage reading. That is after sitting overnight and opening the door and maybe turning on the headlights WITHOUT putting it into "ready" mode.

    Also just disconnecting the 12 V will reset some codes.

    You won't have a good handle on this without some additional measurements AND probably waiting a couple of weeks to see if it comes back or not.
     
    #2 sam spade 2, Feb 10, 2020
  3. rjparker

    rjparker Tu Humilde Sirviente

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    You may have something wrong in the hybrid system which triggered other things that are not bad. The best thing to do is wait for another check engine or check hybrid system and check codes at that time.
     
    #3 rjparker, Feb 10, 2020
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    @Merv Himself

    are you able to post a photo of the "crack"ed negative terminal?

    disconnecting the 12v (-) cable is a very effective way of resetting all the ECU's to default values and clearing codes :)
    unfortunately, it also prevents being able to use a code reader to perform diagnostics.
     
    #4 TMR-JWAP, Feb 10, 2020
  5. Merv Himself

    Merv Himself Junior Member

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    Guess I better gear up with a code reader then. Any affordable suggestions would be greatly appreciated.
     
    #5 Merv Himself, Feb 10, 2020
  6. Merv Himself

    Merv Himself Junior Member

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    Thank you. Taking the connector off the post is such a delicate trick that I'd rather quite while I'm ahead. But if it helps, I'll give you a better description. That post kind looks like if you took a pipe and bent it back & forth until a crack formed. Strange enough though, seems to be conducting electricity just fine.
     
    #6 Merv Himself, Feb 10, 2020
  7. Merv Himself

    Merv Himself Junior Member

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    Yeah, I figured I had done a reset, but also figured if it was a real problem the warning lights would come back on, which they haven't. Last time I had this problem was about 5 or 6 months ago and it hasn't occurred since. Then it happened again today. Of course, my curiosity and concern wants to get to the bottom of this before it happens again. What should the voltage read after the overnight procedure you just mentioned?

    Thanks for your help.
     
    #7 Merv Himself, Feb 10, 2020
  8. TMR-JWAP

    TMR-JWAP Senior Member

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    Something to watch out for. A damaged post like that may conduct voltage just fine. Even a component with a million ohms resistance will pass full voltage if there's no current flow (like when there is no load), but the voltage on the load side of a high resistance connection will effectively drop to zero once any current is attempted to be drawn.

    If that crack is a high resistance connection (and it likely is) any significant current draw will GREATLY decrease voltage available to the 12v system. Even a mere 1 ohm resistance connection, with a 5 amp draw, will drop the 12v down to 7 volts on the downstream side of the connection, while the battery side stays at 12v

    Anything you can do to make that connection/crack better, will pay off.
     
    #8 TMR-JWAP, Feb 10, 2020
  9. rjparker

    rjparker Tu Humilde Sirviente

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    The Optima battery uses cheap hollow battery posts that are easy to crack. I had one like that but it worked fine, especially since the inverter takes the load after going to Ready.
     
    #9 rjparker, Feb 10, 2020
  10. Merv Himself

    Merv Himself Junior Member

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    That was my take on it, too. Everybody raves about those optima batteries, but I thought those posts were pretty cheesy. Like you said though. It seems to conduct electricity just fine.
     
    #10 Merv Himself, Feb 10, 2020
  11. Merv Himself

    Merv Himself Junior Member

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    Good tip. Thank you. It's weird how sanding it and hittin' it with a wire brush seems to cure this problem, but like you said maybe I am just improving it ever so slightly enough to make a difference. Been thinking about just buying a new battery since this one is going on 4 years now.

    Any other suggestions before I take the plunge and shell out $200+ bucks?
     
    #11 Merv Himself, Feb 10, 2020
  12. sam spade 2

    sam spade 2 Senior Member

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    A completely charged AGM battery that is healthy should read 12.7 minimum with no load.
    It should not drop more than a couple of tenths after the car "wakes up" but before put into the "ready" mode.
    So that would be 12.5. Maybe another tenth with headlights on.

    P.S. Those voltages are AT the battery posts.
    And.....if your description of the battery post is accurate, that is it looks like one or two more bends would cause it to break off completely.......I suggest that you start looking for a new battery.
    And probably NOT an Optima.
     
    #12 sam spade 2, Feb 11, 2020
  13. sam spade 2

    sam spade 2 Senior Member

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    Get the OEM part number and "generic" equivalent "type" number and then shop around.
    While the OEM ones are good, you should be able to easily save about $50 on the battery itself and with "free" installation maybe another $50 on labor.
    I think Pep Boys is most often mentioned as having good replacements.
     
    #13 sam spade 2, Feb 11, 2020
  14. Merv Himself

    Merv Himself Junior Member

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    I think you're right, Sam. That post folded like a cheap suit. Unreal
     
    #14 Merv Himself, Feb 11, 2020
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