Power Button Not Working after Dead Battery Reverse Polarity

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Vintess, Aug 16, 2021.

  1. Vintess

    Vintess Junior Member

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    Hi All! I need some help.

    Here is the major details. Upon taking the car cover off of my 2014 Prius Four, I discovered a dead batrtery. I took my DieHard Battery Charger out and hooked it up. Then noticed the red light on the charger, indicating a problem. I looked at the battery hookups and noticed I accidentally reversed the cables. I correct the hookups and proceeded to charge the battery.

    Upon the completion of the battery charge, I tried to start the car. When I depress the brake pedal I get a message on the dash screen that says to depress brake pedal and hold key to the power switch. I do that and the same message comes up and car does not enter the startup procedure. Apparently, either the power switch or the brake pedal circuit has an open. Also my key fob is not working at all. Cannot lock or unlock doors, etc.
    I have checked all small pullout fuses under the hood. I

    'm attaching a pic of the underhood fusebox. I have watched youtube videos that shows the fusible link with the cover off, but mine seems to not have a removable cover so that I can see whether a section has blown or not. IMG_6241.jpg

    I've read articles and watched youtube videos that related to a "fusible link" failure after a reverse polarity event. But, I don't mind going over to the Toyota dealer and buying a fusible link modele, but Iwant to make sure that is the insure before shelling out major coin! Anyone know about how much these fusible links are?

    Any help would be greatly appreciated, as I am at my wits end on this.
     
  2. tankyuong

    tankyuong Senior Member

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    Should be around 100bucks
     
  3. Vintess

    Vintess Junior Member

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    Tankyuong, many thanks for the reply. I already ordered one. $120 skins in SoCal. We always pay more in Cali! much appreciated, Thx!
     
  4. bisco

    bisco cookie crumbler

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    i'm not sure a charger will blow the link

    do the brake lights come on when you step on the pedal?

    does the red light on the fob come on?

    do you have a voltage tester for the 12v? is it original? you might just need to replace it.
     
  5. ChapmanF

    ChapmanF Senior Member

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    Sounds like you've been looking at pictures of Gen 2 fuse boxes, which have a long multi-fuse module down the side. In the Gen 3 fuse box, what you see there isn't that at all, it's the Integration Relay. It's probably ok.

    Given that you reversed polarity, not with a powerful jump battery, but with a current-limited battery charger, it seems unlikely that you blew any large fuses (like the 125 amp one that is an enormous pain to get to). It is possible you didn't blow any fuses at all, or some smaller ones, if any. You might have scrambled some memory in an ECU somewhere.

    Have you checked the fuses under the dash?

    Have you unplugged that fat white wire in the underhood fuse box for a minute or so, plugged it back in, and tried again?

    What was the current setting on the DieHard charger?
     
  6. Vintess

    Vintess Junior Member

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    Bisco, thank you for the reply. Yes, I agree, it seems unlikely that a microchip-controlled battery charger would cause a fuse to blow. However, this has me scratching my head. Something happened related to the dead battery and subsequent reverse polarity hookup that has caused the car electronics from recognizing the key fob and the push start button from lighting up. Yesterday evening, the Charger was able to charge up the battery to 92% and which point I unplugged it because it was getting too dark (late). I haven't checked the battery status today, but will do so tomorrow morning.

    As soon as I get a chance I'll also check the brake light functionality. Yes, when I depress the fob buttons, the red light does come on. I assume that this means it is working and sending a signal out. I do have a DMM and will check the battery status. I actually was thinking about replacing the battery, as it is about time and didn't want what happened, to happen. I know it is a slight hassle when a Prius has a dead battery! I have already priced out an Optima Yellow Top AGM and will probably pick one up tomorrow.

    Again, many thanks for the input and I will keep adding to this thread in the hopes of helping someone else out down the road.
     
  7. Vintess

    Vintess Junior Member

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    ChapmanF, thank you for educating me and readers on the Gen3 differences related to the under-the-hood fuse box and, in particular, my issue. No wonder it looked so different...

    I have not checked any underdash fuses. Good suggestion. I'll do that ASAP. I will also do the white wire unplug-plug routine, as you suggested. The Diehard was set at the 12V-AGM charge setting. As I stated above in another reply, something happened that is causing the car's electronics to not recognize the key fob. Likely culprits are the power button circuit, brake pedal circuit, or, as you suggested, maybe the reverse polarity has scrambled the memory?

    I'll see if I can hook up the laptop with Techstream to see if I can locate the issue(s) on Wednesday. I'll keep the thread posted of any progress.

    Again, many thanks for your reply/input.
     
  8. Rebound

    Rebound Senior Member

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    Did you try to pull the 12V battery ground and then reattach?

    I wouldn't buy a new fusible link unless a continuity test proves that it's blown.
     
  9. ChapmanF

    ChapmanF Senior Member

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    I also wouldn't buy an integration relay thinking it was a fusible link, but the order might have been placed already.
     
  10. Vintess

    Vintess Junior Member

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    Thank you all that have contributed your thoughts and expertise. I was able to do some more troubleshooting early this morning before I headed out to work.

    Yes, of course, now that I know that what I thought was a fusible link under the hood of Gen 3's is not that, I will return the ordered part. Thanks, ChapmanF and Rebound.

    The following is what I have discovered/done.
    1. All pullout fuses both in the engine compartment and underdash fuse boxes are okay (I conducted continuity tests).
    2. The brake lights do work when the brake pedal is depressed.
    3. The dome lights work when I open the doors.
    4. The security system chirps when I lock the driver door via fob pullout key.
    5. The door locks work from the inside.
    6. I have pulled off the negative cable from the auxiliary battery. However due to time constraints, it was only off for approximately 3-4 minutes).
    7. I did, as suggested by ChapmanF above, disconnect the thick white wire from the underhood fuse box, but not for very long.
    8.The auxiliary battery voltage is 11.9V and appears to be okay, although not fully charged. I'll hook up the charger tomorrow and get it up to full charge.

    I am beginning to think that the reverse polarity event did scramble some onboard memory (as suggested by ChapmanF) somewhere and affected the fob registration code. I going to try to link up a Chinese bootleg copy of Techstream (it's about time I tried it out; it's been installed on my laptop for months) tomorrow or Thursday to see if there are any fobs registered and to see what the diagnostics data says are the issues, if any (other than the unrecognized key fob). All things so far point to the key fob not being accepted by the onboard electronics, as most things that don't go through the power (ignition) keyless switch appear to be working normally and no fuses have blown, that I have discovered in the two fuseboxes tested so far.

    Does anyone know if there is a fusible link attached to the positive pole of the auxiliary battery? Also, anyone know where on the car I can take a reading of the hybrid battery voltage with a DMM, just to make sure some fusible link in that circuit has blown?

    Thank you all who have contributed. You guys are the best!
     
  11. Rebound

    Rebound Senior Member

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    11.9V is quite low.
     
  12. ChapmanF

    ChapmanF Senior Member

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    These have the same effect. I only suggested the white wire unplug because it's easier than fussing with the battery in back.

    There is, but it is clearly ok, or all the test results you have reported here would have been different.

    At this point I would say there is not enough reason to suspect that to justify the personal risk. The car is bailing out in the power-up sequence somewhere before it brings the traction battery online anyway, so everything important to check seems to be in the 12 volt system.

    Once you get Techstream hooked up, you should be able to ask what the traction battery voltage is.
     
    #12 ChapmanF, Aug 18, 2021
    Last edited: Aug 18, 2021
  13. Vintess

    Vintess Junior Member

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    Okay, I've made some progress. Still not there, but inching closer.

    Here is what has happened today. First, I disconnected the negative wire on the auxiliary battery and finished up the charging process. In doing so, I suspect, the fob code came back to life somewhere in the car's electronics. I am thinking that the time the car was without 12V power, the system must have reset? Anyway, the fob now works and the car starts up. However, a new issue has surfaced.

    In starting up the car, there is now a notification on the dash screen that says that there is a problem with the hybrid system and to pull over in a safe place! I am thinking that the hybrid system's fusible link at or near the hybrid battery has blown. Any thoughts?

    I am no Techstream wizard by any stretch... In fact, today was the first time I have used it. I was able to dig around and discover that there are two DTC's that surfaced: U0100 (Lost communication with ECM/PCM "A") & U0129 "Lost communication with Brake System Control...". Any thoughts what this may mean?

    Since the car was without 12V power while the battery charge was going, there were "incomplete" results on many of the systems. The above were the only trouble codes I was able to uncover, although there may be more that I missed. Again, I am a newbie with Techstream.

    Again, many thanks to all that have helped me in trying to figure this thing out.
     
  14. rjparker

    rjparker Senior Member

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    Does the engine start? The car won't start the engine without the hv battery.
     
  15. JTR1977

    JTR1977 New Member

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    Hi dude you are describing my exact problem....have been s#$&&*%g bricks thinking i am looking at major $$$ to fix problem for the last 10 days..... i bleed the breaks charged battery bought diagnostic tool ( witch didnt work btw) and 10 min ago i took battery out of fob( as it wasnt working) then noticed the lights (on fob ) lit up.... went out side and unlocked car with fob and jackpot!!! Car started good as!! no warning lights or anything!!! So maybe all you need is a new button battery for your fob? Hope this helps !!
     
  16. Vintess

    Vintess Junior Member

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    Yes, the engine does start. The steering wheel is as stiff as a skyscraper I-beam. I have not driven the car, nor will I until this is all sorted out. I'm thinking that I might have missed a blown fuse somewhere. I'll retrace tomorrow and religiously do a continuity test on all pullout fuses, again...

    I did read a thread here on this site about a the so-called "Integration relay" (underhood fuse box) being bad related to one of the DTC I found. I'm not sure if this integration relay is part of the traction battery circuit (hybrid system), but I would guess that it is. It looks pretty beffy and has large gauge wires attached to it.

    Thanks for your input... If you think of anything, please respond...
     
  17. rjparker

    rjparker Senior Member

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    Don't forget the 11 other fusible links including the electric power steering

    4DB1C5DC-10EC-4BAC-A9BB-CCE8D240809A.jpeg
     
  18. ChapmanF

    ChapmanF Senior Member

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    Highly unlikely, and in fact completely ruled out by your later post confirming the engine starts.

    People have a funny habit of having heard there is such-and-such a part in the car, and then guessing the problem might be that because it's a part they've heard of. There are a bunch of things in the car you haven't heard of too. It is best just to read the trouble codes, look up what they mean in the Repair Manual (more info), and follow the steps there to discover what's up.

    In this case, with the power having been interrupted and memories cleared, the steps could be very simple.

    Often the one-liner "fortune cookies" you find for trouble codes aren't very useful on their own; where you find what they are really telling you is in the full Repair Manual section for each code.

    For these communication codes (which all U codes are), the fortune cookie pretty much gives you the gist. Whichever computer in the car reported the U0100 isn't able to talk on the car network to the engine control module, and whichever one reported the U0129 isn't able to talk to the brake module.

    You'll notice I said "whichever computer reported ..." a couple times. When you do a Techstream health check, the results screen isn't just a list of codes; it also tells you which computer reported which code. That's information you should pay attention to, especially for U codes. It takes two to communicate (or fail to communicate), and there are different computers in the car that could all say U0100 if they can't talk to the ECM, or U0129 if they can't talk to the brake ECU. So to know who is failing to communicate with who, you also need to pay attention to who gave which code.
     
  19. Rebound

    Rebound Senior Member

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    If battery voltage is only 11.9V, that’s the first thing to fix. Replace the 12V battery.
     
  20. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I’ve probably gone here before, but:

    Is there any way to avoid the cascade of blown fuses and possibly fried components, to nip a reversed 12 volt jump-start connection, say with one heavy-duty fuse at the head of the line? Impractical, too expensive?
     
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