Dead 12V leading to Check Engine Light

Hi All,

I'm having trouble with my 2008 Prius. I've searched the forums and seen similar issues but really need help with my particular situation.

Long story short: 12V died twice (replaced twice, first time gas gauge bugged, 2nd time won't start and shows check engine light, but no other lights).

Details:

80k miles, no problems except for the 12 V repeatedly dying several years ago, which seemed to be fixed when we turned off all the door lights- looked like our young children were closing the doors partially, draining the 12V, or so we thought!

1. I'm in the process of leaving France for Canada and had to leave the car a couple of weeks to handle the move. I was supposed to come back 2 weeks later, but it ended up being 5 months.

When I got back (Dec 23), the 12V was dead. I jumped it, took it to get new one (it had been pulled down to too low to recondition), but they didn't have a gel battery to replace it.

They gave me a less powerful model and it worked fine. I wasn't worried because this car was going to be gifted to a nephew upon moving, he could buy the gel 12V!

2. I had to go back to Canada for 2 weeks, came back, battery was fine. I drove it fine for 2 weeks until I realized the gas gauge wasn't going down... Thought that was weird, went to the gas station and filled it up with 10L gas...

Looked on Prius forums and saw this was kind of common and tried to do the weird code thing to reset it but never got it to work...

I saw you could also just unplug the 12V for a while and planned to do that once I got the tools (mine are all in Canada now!).

3. I drove it 5 days ago in very cold weather and all was fine. Then yesterday it had all the signs of a dead 12v. Couldn't open doors or trunk, etc.

Crap.

Do tried to jump it and 2 weird things happened:
1. had to press the power button twice while breaking to get anything to happen. On first it did nothing.

2. On second press, it started making the whirring pump noise it always does on start (but no engine noise), and showed the "check engine light." (and power light turned orange).

No matter how I tried to jump it, that's what it did. I have never had any lights at all on this car!

Also, I tried to recondition the battery with a CTek charger all night, but it seemed the battery was too low since it didn't advance to the final stages (I don't have a 12v gauge here).

I read some people had weird issues with their Prius dead 12v that only resolved with new batteries, not just a jump.

So I got a neighbor to bring me a new 12V (correct size) today.

Now: I replaced the 12v and it now it reacts on the first press of the power button while breaking (power button turns green, but no other reaction).

On second press of the power button while breaking, the power button turns orange, check engine light (and only the check engine light) turns on, whirring starts, but nothing else.

I also can't turn on any of the lights in the car...

It's all very bizarre!

I'm hoping that this is just some weird error code situation like what was happening with the fuel gauge.

Any help is greatly appreciated!!!!

I need this car for another month and then will give it to a nephew. I already paid 300 euros for a new 12v battery.

If I have to spend much more money to get it fixed, it's likely cheaper to sell it for parts and hope that the price covers rental fees for the next month.

Such a waste for a great little car!

Merci beaucoup!!!!

 

Update: I found this YouTube video that looks exactly my issue (the whirring is the "brake actuator")

The author says to check the main fuse.

I checked, and sure enough, it's burnt!

It looks I might have reversed the jumper cables??? I'm pretty sure I double checked, but I'm also incredibly jetlagged, so all is possible!

I have to find a way to buy a new one tomorrow and will update here.

From the comments in the video, this issue is pretty common so I hope my video helps someone!

It was 3 weeks to get a mechanic appointment for a diagnostic, at which point I will have left France permanently. I'm thrilled I might not have to junk a great car!

Cheers!