Help Diagnose Electrical break down while driving?

First the brake light came on after abut 1/2 mile of driving, (like the parking brake was on). I pulled over to check fluid but it was OK. Started up again and same thing after about 1/2 mile. Next a warning whistle came on along with the light. Then the brakes started behaving funny. The pedal felt hard and if I put on the brakes when creeping a few mph the brakes would make a bit of a grinding sound and the car would rock a bit. OK, enough on the brakes. I don't think the brakes are the problem but rather a symptom.

Next the yellow warning lights come on a few minutes later. Then a minute later the red triangle lights up, Followed by a message on the main display, something about "locked" and "parked", (don't remember exactly). I checked to see if I was in park and no, I was in Drive. (I was still driving at this time). a few seconds later the car goes into neutral and I coast to a stop. all the green lights for fuel, gear mode etc are now blinking at me. I put on the emergency flashers and both are blinking but sometimes only one. I go outside and the blinkers are very dim.

AAA comes and needs to be able to roll the car which has locked itself in Park once I turned off the power. He hooks a battery up to it to get me started (would not power up on its own) and it all looked fine. He followed me to my mechanic (where I was heading anyway LOL)

I figured after all this it was just a bad 12V battery. After all the battery is going on 11 years and 215K miles!

Today the shop calls me and tells me that the battery isn't testing all that bad, but just a little low, not low enough to cause the problems I experienced. They cannot reproduce the failure that I had. They did find a few stored error codes that indicated a low voltage situation. One was the ABS. The shop isn't convinced that the battery was the cause of the low voltage codes because the battery isn't testing bad enough. BTW the AAA guy didn't charge the battery, he just gave it a quick jump after which it sat all day and last night. Plan now is to replace the battery anyway and see if it happens again. I really want to avoid a repeat because I often drive up the Northern CA coast and have no cell reception and am hours away from a tow.

Any ideas would be appreciated. One other thing is a couple times in the past few years I was driving and all the dash lights came on. I pulled over and powered down and when I started up again all was fine for another year or so. These events did not show up in future code checks.

Thanks for reading!

 

That's the plan for now. I hope that takes care of it. Thanks for the encouragement that it might just be the battery. Thats my gut diagnosis too but maybe I'm just an optimist

 

Good point about the charging. I will give them a call and ask if they checked that.

THanks!

 

Its at a good shop but not a dealer so you might have a point there.
Thanks

 

Yes it is being replaced as I write. But, really I was quite fond of that battery for lasting so long. I might just have to keep it on display somewhere in my house. LOL

I called the Toyota dealer and he said that pretty much any shop has the ability to read and understand prius codes for the engine and hybrid system, and that the Prius specific codes that the dealer has are "body codes" (whatever that means). The dealers advise was that if the battery is replaced and no codes show up after clearing the codes and a good drive that I should be good to go.

 

If there is a charging issue, would that throw a code?
Thanks

 

Thanks All for your helpful input. I have my car back with new battery, so we;ll see how it goes. Also finally after 215K miles it was time to replace the front brake pads. My sons Honda needs the every 30K or so and he drives with a light foot. Love that regenerative braking!