Electrical Issues - how to further diagnose?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Johnson54, Jun 19, 2021.

  1. Johnson54

    Johnson54 New Member

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    Hi everyone! I'm a new poster to the forum, so apologies if something similar has been posted before. I've read through several related posts, but none exactly the same.

    After work on Wednesday, I got into my Prius (2011) to head home. There was no response from the dash, including no aux light on the start button. After a few minutes of finicking around, I got it to start by placing the fob close to the start button. I figured the fob was dead (although I hadn't seen a warning notice) and replaced it. The next morning starting up, same issues. I started getting strange noises from the brakes, and cycled through no response to aux a few times before getting the car to start.

    Today, I pulled and checked each of the fuses in the fuse box - and all were fine. Still no response and start up from the car. My husband pulled a white cable in the fuse box for two minutes and replaced it - I think it comes from the 12v battery. The car did turn on normally, with all dash lights showing up appropriately. Also, I was changing the display to see the battery reading, and the tracer display from the steering wheel showed up - which I haven't even ever seen. I bought the car used in 2019 and didn't even know it was a feature. ???

    This seems like there was some sort of reset, but I'm unsure. What does this issue sound like to you guys? An electrical short? Hybrid battery? Appreciate any and all help! I am completely stumped - and scared to drive my car!
     
  2. tankyuong

    tankyuong Senior Member

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    Test the 12v battery
     
  3. Johnson54

    Johnson54 New Member

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    Sorry for the delayed response - had to go out and buy a voltmeter today.

    When off, the 12v battery is reading 10.8. I'm assuming that means it's dead. If that's the issue, I'm happy to replace it and check back!
     
  4. JohnPrius3005

    JohnPrius3005 Member

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    While the 12 v bat may not be dead, the consensus appears to be that it might be suspect. It's possible to fool around with it, and recharge it, and it might be fine. But the quickest way is to just get a new one and charge the new one fully and replace the old one (don't assume that the new battery off the shelf is fully charged). If you're impatient you can assume the new bat is charged and just install it (that's what I do) If you /your husband are at all handy it's preferable to do this yourself, rather than to let anyone else loose on your car, who may or may not know about Priuses. Once the 12 v bat is replaced by a new fully charged 12 v bat you can start the car and drive like normal. It's possible you have to push the power button more than once to get the car going. You'll have a lot of warning lights and they will generally go away once the car "resets" or "reboots" all the computers. (the sequence for this if you have to do it is: attempt to start the car like normal. if it doesn't start like normal, don't push any buttons including the power button, wait say 20 seconds, and again push the power button as if to start the car. it should then start. if it doesn't power the car off with the power button. Then try to start the car like normal. Again it should start).

    Others on here are much better at describing the above procedure than I am.

    Of course you might have something draining the old (and then the new) 12 v battery, so the age of the old 12 v bat, and how much you have been driving of late, should factor into your decisions.

    There is also I understand a way to attach a known good 12 v battery, or 12 v source, to the under the hood jump terminals and avoid the various transient issues which arise by disconnecting 12 v entirely from the car, but you want to be careful because this may mean the positive wire to the old 12 v bat is hot while you install the new 12 v battery. And if the fob is anywhere nearby the car might start.
     
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  5. Johnson54

    Johnson54 New Member

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    Thank you so much for the help! Apologies for the delayed response, due to work, yesterday evening was the earliest I was available to grab a new 12v.

    This did resolve the issue! Husband and I got it changed out with no issues in just a few minutes. The car did need to be started up twice to get going, as you mentioned, but we took a drive right after and it did just fine. Thank you so much!

    The engine did make some really strange/loud rattling noise upon first starting up, that I've never heard before. I'm hoping it was just weirdness from having sat for a few days/repeatedly trying to restart the car. I'm not sure.

    But thank you for the help with the battery regardless!
     
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  6. bisco

    bisco cookie crumbler

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    congrats on the fix.

    about the rattling noise: your car is subject to clogging of the egr system. this can lead to a blown head gasket, which has become very common in 2010-2011.

    there are many threads here on how to clean it, and also youtube video.

    all the best!(y)
     
  7. Grit

    Grit Senior Member

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    replacing the 12v bat was just a stroll in the park. As for the rattling, you’re in for a treat.
     
  8. Johnson54

    Johnson54 New Member

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    Thank you for the info! Looks like I'll have a busy Saturday today, then!
     
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  9. Johnson54

    Johnson54 New Member

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    Hopefully husband can be bribed into helping me again today......
     
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  10. bisco

    bisco cookie crumbler

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