2007 Prius Turning on By Itself

I don't believe this particular issue has been reported before. You are correct that an intermittent problem like this will not easily be serviced at a dealership.

What is your exact procedure to turn off the car and lock it?

How far is the Prius fob kept from the car when this mysterious behavior is going on?

I think the power source control ECU is having a problem.

 

Your power down and locking procedure appear to be fine.

You may need to disconnect the 12V battery while the car is not in use, until you figure out what is wrong with the car. One way is via the hood: open the main relay/fuse box, find the dedicated jumpstart terminal under the red plastic cover, and use a 10 mm socket to remove the nut there. Pull up the wire attached to the stud, which will disconnect the positive side of the battery. Reverse that procedure before starting the car.

 

Never heard of this. The car is going into ACC by itself. Which means the Immobilizer ECU/circuit is not working in addition to going into acc by itself. Hard to believe. Does the dash show a blinking red car icon when key fob out of range? Can you go into ACC without the fob in the car. Or does it do nothing and throw a yellow key icon like it should.
ACC is 2 ready button pushes without holding the brake down.

But to stop why are you holding down the brake and then holding down the power button to shut the car off?

Not necessary to do any of that. When you get to where you want to stop just push the power button once briskly for a second and release. Don't hold it down. And don't need to go into park.
The car will shut off. It automatically puts itself in park.

First thing you need to do is replace the 12 volt battery. Its probably really low and very strange things happen when the battery gets low.
That and jump starting a Prius is really bad as hundreds of posts here with people causing major damage to the car jump starting it. Major damage in the $4000 range. Do all you can to not have to jump start this car.

Upon boot up you may not have noticed the dash throws a big red exclamation point for a second. Thats the only warning you get the 12 volt boot battery is on its last legs.

 

Whoa, ghost in the machine. Sort of an X-File kind of thing. Do you have control over both of your fobs? Somebody could be messing with you.

 

I agree that the 12V needs to be checked, or else put the car on a battery minder/charger. The fact that the radio and clock get reset says the 12V has gone too low. This may not be the whole issue, but does need attention.

 

is it the original 12 volt?

 

I wonder if holding down the POWER button is causing the problem. Lots of gadgets perform a different function when held down for several seconds. Maybe over the years the contact is worn and when you hold it down its actually making a breaking connection many time. But this is all just speculation.

Maybe just put in a new power switch.

When ever I turn my car off or on I just press it for about 1/2 of a second. 2008 with 56k miles on it.

 

Is the car's name Christine?

 

aren't there a lot of military installations in south dakota?

 

Did you figure out your problem?
I have a ghost starting 2004 model Prius with 190k.
Please skip the "how did you power it down?". My last 3 prius's have been junk yard finds. I put over 12oK on a 2005 model that I fixed. It has over 300k (speedo stopped reading at 299,999). It is still going strong. I bought the car with the ghost issue from a salvage yard in Austin. It died on the owner and one of the local dealers wrote an 8K dollar estimate to fix it. They had put 2800 into the battery 4 months before and were told it needed and inverter and a transmission. They didn't feel it was worth fixing and sold it. The salvage yard offered more than the dealer. I have no idea what they paid for it, but I bought it for $1900. I replaced the inverter coolant pump, the crank position sensor, and the starter battery. The "bad" trans and inverter have been working smoothly for the last four months and over 7K.
- Last night I came home and shut the car off like normal. I was getting some stuff out of the back seat when it powered back on. It had obviously been off because it was dark and the headlights were out. When it powered itself on the headlights lit up the garage. I powered it down and this time it stayed off.
- This morning I got in it and I had to press the start button twice before it would power on. I drove it 30 miles and stopped for coffee. I powered the car down and the dash lights went off but the radio and the center display stayed on. I pressed the start button to shut it off and it powered back on even though my foot was not on the brake. Thinking I might be getting false signals because of a weak battery in the key fob I turned off the smart feature.
- I then drove 10 miles. When I stopped the car I hit the power button and pulled the key out of the dash. I got out of the car and got some stuff out of the back. I then used the key fob to lock the car since the smart feature was disabled. I was walking off when I heard the engine start. The car had powered up again. This time with the smart feature turned off and the key fob in my pocket.
- I made 8 stops after this and twice the car powered back up on its own. This was the only issue. Everything else worked fine.

I haven't started trouble shooting it yet. I would start with the power button, but how could it start with out the smart feature on?
I also thought that maybe I had mice get in the wiring. Again, how does a car with out the key fob in it start up? Nothing makes sense.
Unless a ghost moved in.
The one car a person never has time to work on is their own.

 

you probably have a bad combination meter

 

What did you find out?? I have a 2005 Prius that just started doing this.

 

I have a similar issue. I have not read this entire, long thread. I do find it very annoying when people sat stupid things like. TURN IT OFF PROPERLY.

My issues began with the black screen problem. NOT THE TOUCH SCREEN. Starting the vehicle would rest in no speedometer no odometer no lights at all ( like none). We get around this by pulling the little white plug in the trunk for 20 seconds.

Recently, we have had dead auxiliary battery problems requiring jump start. A week ago, we were sitting in the car and it turned itself on. No we were not sitting on the key. We were on our phones, internet cruising. We immediately set it to require key insertion to start, yet it will still spontaneously start. Are there any solutions for this? It sounds dangerous, what happens if it next goes into gear on it own, without us there?

 

what did you find to be the answer here? i also have a 2007 Prius with about 170k miles...it is also turning on by itself after properly powering down. Replaced the original 12v battery about 12 months ago. This problem has been happening now for a week. Any ideas?

 

Try arming the alarm every time you get out. See if it turns on then.

 

I cleaned the (2) connectors with Deoxit and reinstalled the battery. The Positive terminal was loose. This required some Dremel work as the clamps can't seem to handle a little extra loss of diameter due to battery age. It has not auto started since then.

 

by "arming the alarm" do you mean locking the door? pressing the 'alarm' button on the FOB triggers the alarm.

 

i took another look at the battery and made sure the connectors were fine, i made sure the connections were snug and secure. however, i found the 'battery exhaust' was disconnected. not sure the overall impact of this disconnection, but i reconnected it, made sure it was secured and will monitor, report any new findings. thank you