Is the 12v going? Need a 2nd opinion

yep... seems like 12v... Your voltage from it is low enough to cause all those symptoms...

 

11.9 when not "ready" is not good. It's possible that you have a loose main battery connection too.

The higher readings you got were from the charging system which keeps the battery charged.......and means nothing about the battery itself.

 

how many miles on her?

once you've eliminated the 12v, check the inverter pump and have the codes read by someone with tech stream.

 

Check the 12 volt battery directly, when the car's off, with a digital volt meter. Think I'm going to make this my signature.

 

yeah, the whole 12v check process should be a sticky in every generation.

 

the problem is, the car has to be using some electricity to give you a reading.

check your voltmeter in the morning before touching the car. it sounds bad to me.

 

probably not. get the 12v taken care of, and then see what happens.

 

sam means the 12v at both posts, plus the negative ground to body connection.

 

Inverter pump code on my 07 Prius was easily read at auto parts store when I was on a road trip once... So I doubt that code is gonna be hiding somewhere.

 

Low battery voltage makes computers do strange things. Take it to the auto parts store and have the 12 V battery tested.

The 12 V. battery is always a good starting point on a Prius.

 

You can totally trust the MFD, to be a good solid fraction of a volt different from a reading at the battery.

There is no mystery to it. The MFD is reading you the voltage at the MFD. There are wires, junctions, and fuses on the path in between, and they all have resistance, meaning they all drop some voltage when current is flowing across them.

You can see that in ACC, the reading at the MFD is somewhere around 0.6 V lower than at the battery, and when you switch to ON, the difference is closer to a full volt. More current is flowing in ON than in ACC.

You can also see the effect reverse when you go to READY. Now the current is flowing from the converter, at the front of the car, to the battery. The MFD is now about 0.6 V upstream.

By the way, your readings are darn close to what I would get if I went out to my car right now and took them, and I am feeling zero concern about the condition of my 12 volt battery. I won't change the opinions of those who are sure the difference between 12.72 and 11.98 volts will make all the car's computers sing "Daisy, Daisy", but I'm not of that opinion myself.

-Chap

 

^^^ I'm in total agreement with Chap.

I find it immensely amusing that we're are at post #16 and only discussed is the 12 V battery. Not surprising that this is not the issue.

There is so much FOD with the 12 V battery. It is not rocket science to test and decide whether the battery is good or not. It shouldn't take 4 people 16 posts to say not much.

What I'm wondering, is what OBDII scanner you are using that turns up no codes when you have lights that indicate there are diagnostic trouble codes stored and symptoms there is something not right with the car?

 

Sorry, bad wording.

Check the main (fat) cables going to the 12 V battery; BOTH ends of both cables.
And that means, disconnect, clean and re-attach. Looking and tugging doesn't count.
Disconnect the negative cable at the battery first and LEAVE it off until the other ones are done and then reconnect it.

Unless your battery is over 5 years old, you might want to complete the above BEFORE you buy a new battery.

 

You are welcome to your opinion but the fact IS that 11.98 with a light load indicates that the battery is HALF DISCHARGED and experience tells us that a Prius might not "like" anything below 12. When it goes "ready" it probably is lower than that.......but it's hard to get that measurement because the inverter kicks in and you see the charging voltage.

 

Actually it is more like urban legend. My real observations on a Gen 2 Prius is that it is not really bothered until significantly lower than 12 V. Sure the battery needs to charged at that level, but then that is a different subject.

It is actually not that difficult, you just need to attach a voltmeter and observe it while starting the car. If more people actually captured real live data, rather that endlessly parroting what they read on the internet, then perhaps some of these battery myths would die.

But oh well, another post that does not help the OP. What are we up to now? Post #20?