2008 Prius will intermittently not start (battery is good)

No fault codes? If there are some what do freeze frame look data in them look like? Maybe there’s bad connection somewhere in 12V system? Does it do the same thing with ley in slot and without? Or do you have the model without the SKS?

 

Everything you describe are classic symptoms of a weak 12V battery. I don't care what any mechanic or dealer has told you, your 12V battery is weak/dying or there is a bad connection. I am very confident it is the former. Mechanics/dealers are notorious for misdiagnosing or identifying a weak 12v battery in a Prius.

If you got a "brand new" battery and this is still happening, the battery is bad or the connections are bad. You might try unplugging and reseating the connectors on the positive cable of the 12v battery (these are white plugs just down the cable).

 

welcome!
agree^^^ is it the original battery? if so, just replace it, it's gonna die soon anyway.
if not, you really should do a definitive voltage/cranking amps test if you don't want to just replace it. you can also check the battery cable connections, especially the negative to body.
another thing would be to back up against a wall or have someone watch your brake lights, to see how hard you have to step on them. the interlock switch may need adjusting.
all the best!

 

still worth testing the battery voltage, just to make sure your not on a wild goose chase. some new ones come needing a charge.

 

Bisco is correct. Assuming the interlock your referring to is the brake light switch, the brake light switch can really be ruled out because the error you're getting says to put the car in park. That is because the "Park" signal to the ECU is so weak, the system can't read it as being there (which is a classic indication of a weak 12v battery or a loose connection).

 

I had the p lock message on my 2005. I believe it's due to moisture getting into the shift actuator. My car ran, but maybe there's a failure mode where the car believes it can't safely start. http://priuschat.com/threads/there-is-a-problem-with-the-transmission-p-lock-mechanism-when-road-is-wet.157165/#post-2283296

 

I had very similar symptoms in my 2008 -- it would intermittently have no power to anything, only after it was parked for a bit. I had replaced the auxiliary 12V about 14 months ago, and it still showed 12.3 V at the terminal under the hood. Last week I checked it's connections and the positive terminal connection was a tad loose. Tightened that up and all is good, so far. I guess it took 13.5 months to loosen up.

 

The definitive test is to get a voltmeter. Buy one. Open the hood take the black plastic cover off the fuse box on the right. Flip open the little red
Cover revealing the 12 volt jump lug. In D.C. Volts measure from their to ground. Write it down.
Then with voltmeter still connected while someone pushes the Start button monitor the voltage swing.how low does it go?

You put a new battery in then u split for a week and whatever killed the first battery killed the second battery.

Also a good trick is at night before u start the car turn on the headlights. Then with them on start the car. If they dim or dip down your 12 volt
Is ready to leave u.

You may have light on in the back of the car and it's killing the battery
Or the back hatch is ajar or u have kids getting in the car and leaving
Door ajar.

People with consistent 12 volt issues always have one thing in common.

They don't arm the alarm every time they get out of the car no matter where they park especially final park in garage. That will alert u to light on or door ajar.

 

Kleo,
I know it's been a while, but did you ever get a concrete solution to the intermittent no-start (battery drain) problem? Reading your issues, sounds identical to what my car just started doing.
Thanks

 

The best guess in this thread was post #3.
And that is where YOU should start too.

The most common main battery connection problem is with the OTHER end of the negative cable.

 

sounds kind of like a combination meter problem