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2008 Prius Touring No Start New 12 volt battery

706 Views 6 Replies 3 Participants Last post by  bruceberquist_3929
This car started and drove fine for a month. No warning lights. Red Triangle Light came and check engine light came on Onboard test showed 12 volt battery at 10.6 volts. Replaced the 12volt battery with a new Toyota battery The car started an ran fine with no warning lightsAfter about a minute the red light came back on but the car ran fine The hybrid battery indicator went from purple to green to blue showing six segments Shut off the car and the buzz that usually comes on at shutoff for a few seconds came on for about thirty seconds Now it will not start with brake engine vsc and red triangle light seen in the picture
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You are going to have to get the trouble codes in order to begin to knowcwhere to look for the problems that is causing that.
It really could be a number of things from simple to major.
Get yourself a code reader. It isca useful tool to have as a car owner, or go to a parts store or mechanic to have the codes read.

To just get the car starting again try disconnecting the 12v battery for a few minutes and reconnecting. That will reset ECUs.

Either way your going to have to read the codes in order to knowcwhats going on.
I have a code reader now Using Dr Prius app it shows negative 12.9 v I’m battery block 24.9 block 3 with red indicator bars All other blocks are green View attachment 2527
View attachment 2526
Looking at your battery readings it appears that you are probably going to have to replace those 2 bad modules.
Both an overcharging module and an undercharging module are signs that they are bad.
It appears by the negative reading that you probable have a short or a serious draining condition on that module.

Before ordering replacement cells for those modules I recommend that you disconnect the safety plug and open up the battery cover so you can physically see what's going on.
Such as heavy corrosion, a burst cell, or leakage from cells to the chassis of the battery assembly.

A shorting sensor wire in the harness can wreak havok (I found that out personally).

Pull the terminal connection out from the battery ECU in that assembly and look for burned or corroded pins.

Most likely you have some bad cells in those two modules.

Its really not that difficult to DIY replace those yourself as long as you follow safety procedures and instructions. Or have a trustworthy tech who knows Prius do it. It is far less expensive than replacing the assembly.

Personally, I advocate for the DIY approach.
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Have you put a code reader to it and read any codes? Most of the time, this can help you in finding what direction to look.
Since your car sits at your camp, there is a possibility that mice or chipmunks might be doing some wire chewing. I've discovered by experience that they prefer and love little wires, such as sensor and stereo wires.
One little chewed sensor wire could throw off ECU readings and diagnostics.
An ECU might be sensing a problem when there is none (other than a chewed wire) and is not allowing the system to go to "ready".
There are many sensor wires that can be the culprit.
That is where an OBDII reader reading might help. Not nessicarilly for finding codes but also for getting live readings.
Are there any important sensors, such as O2 or MAF, etc., that are not giving readings?
Just an idea. Chasing ghosts can be frustrating.
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