smart key system

Yes there is a battery in the Key FOB. My 2004 Prius had the same thing just a few weeks back and I replaced the battery and it works fine.

Thank you so much for the advice. Can I buy the battery anywhere, or must I find a Toyota dealer?

It should be a standard cb type battery that can be picked up at any department or hardware store.

What the other gentlemen said about there being a battery in your key fob is true. It can be replaced at any Toyota dealership and possibly at a battery or watch battery store. The other possibility however is that the key fob is not in the sensor range. If you put your fob in a purse and place it in the trunk or back seat, the sensor may not sense it. I have a Prius myself and had the key in the left pocket today instead of my typical right pocket and it had a momentary lapse of finding it.

Most likely it is the battery in the fob. However, we have a 2005 Prius with the Smart Key and we experienced the same problem about three months ago. It only occurred once. I was driving with key in my left pocket and my cell phone rung - in the same pocket. I answered the phone and had a short conversation and hung up - still driving all the while on the freeway. When we stopped about 15 minutes later and got out of the car, the car would not lock using the black button on the door handle. I tried several times, but nothing happened. I then pulled the smart key out of my pocket and pushed the lock button on the fob - still nothing. We could not lock the car! I then tried to start it - nothing. I then inserted the fob into the slot and the car did start. I shut it down and then tried to lock the car. I still could not lock it up using the buttons or the remote. I then removed the real key from the fob and locked the door manually. We returned to the car a few hours later (we went to a recital for our daughters' piano class) and the car recognized the Smart Key and unlocked as we approached and put my hand near the handle. Apparently it had "reset" and all was well again. Later I read the Owner's manual and it states that the Smart Key should be kept 1 meter from other electrical devices such as cell phones, etc. I had no clue. We have not changed our usage of the Smart Key and its proximity to cell phones, etc. and haven't had a problem since. Weird!?!

hi...i totally have experienced the same thing as you guys with a 2005 Prius. i have waited a day but the remove still does not work as i approach the car and still have to put the key it to start. hope it works just fine tomorrow. because i don't think the battery is aging. since i just changed it a few months ago. is there any way to make it goes away faster. love my car ;(