2011 Prius 4 suddenly wont start

Yeah, I realized later Shame on me. Thanks though.

 

If the 12v battery is 8 years old. It's time to replace it. A worn out battery could read good one
second bad the next. A loose or corroded terminal could give the same results.

You can look at the battery. Follow the cable on the right, the negative/ground cable.
It bolts to the frame. It should look new. If not, remove it and clean it with a wire brush, or sand paper.
The positive is on the left. It should look new also. If it's corroded, remove it after removing the negative
cable and clean it.

Even though you jump it, an old worn battery will draw all the current from the jumper, and not allow any,
or very little to go to the components to trip the relays that let the car start.

You could try disconnecting the negative terminal of your battery, and use jumper cables to connect a KNOWN good battery.
This would eliminate the battery completely and the car should start easily. And everything the doors should unlock.
And the brakes should build up pressure quickly.

 

Friends, please stop telling him to buy a new battery before he knows if that will fix the problem, which it probably won't. Maybe it is due for a new one, but that sure doesn't sound like it'll make the car start reliably. Why spend lots of money and time before spending ten seconds checking the terminal connections and ground to the body? Then grab the wallet if you find that it's necessary. If you have a loose connection on the ground lug at the body, you can buy a thousand batteries and the car won't start reliably.

 

We had one feller here that was having key fob battery remote issue and after a few button battery cell changes, he fixed the issue by trading the car in for car payments on a new gen 4.

 

Well, I like my Prime so much more than any other car I've had, I might have done the same thing. There are better excuses for sure, but you take what you can get.

 

Well, doing nothing, next day early morning, empty street, it started. Now I suspect some automatic door opener or some other signal that prevented my start. I will double checkthe grounding too, as much as I can..
Replaced the 8yrs old buttery later, just to make sure. Both fob battery measure fine 2.9-3.0 V.

 

Dear friend:
IF.....the battery is 8 years old, changing it certainly will fix SOMETHING but maybe not what is being described here.
AND.....if the highest the voltage ever gets is 12.3......same thing.
Those who are suggesting a new battery are NOT giving bad advice.......it just needs to be qualified a bit.

 

Not saying it's bad. Just in the wrong sequence for getting out of the crisis. Pick the low hanging fruit first.

 

SIGH.
You have been around here long enough to know that the 12 V battery most often **IS** the "low hanging fruit".

 

LOL! Sorry. I forgot.