I was trying to think of a way to store a programed key fob in my car in the event of a loss of the one I was carrying. The thought is hiding the door key to get into the car, then since the presence a fob in the car screws things up, storing one sans the battery. Then keep the battery separate and having a small jeweler's screwdriver on hand in the car and reassembling the thing when needed. The BIG question is does removing the battery power down the programing in the fob and render it useless until re programed????
I believe there was an early post about wrapping the fob in foil. Don't know if it will work but won't cost anything to try.
Removing the battery will only prevent transmit functions from working until the battery is replaced. It does not affect the programming. Even with the battery removed, the fob can be used to start the car by inserting it in the slot in the dash; there is no need to reinstall the battery for use in an emergency situation.
Agree, if the fob is likely to be used only in an emergency then I'd just leave the battery out and use the key in the slot in the dash when needed. If you want to leave the battery in then you'll need a Faraday cage of some sort. Foil may work, an Altoids can works well (and would disguise the key from a would be thief). One word of caution. I have heard that the way the rolling security code works that after a certain period of time you can "unmatch" (for lack of a more accurate term). I don't remember how many starts it is...maybe 100? So every month or so it would probably be a good idea to use the emergency key just so the rolling code updates properly to your every-day key.
Never, ever, EVER store a keyfob IN THE CAR. It leaves you too many things that can go wrong. a safer bet is to habitualize carrying the keyfob in a coin catch and the key attached separately to your keyring. Then, when the car starts having trouble opening at your command AND you notice the dome light not wanting to come on as you approach, remember to replace the battery. If you're really bent on doing this, then you should pony up a few bucks and solder in a physical switch on the keyfob you plan to store in the car. It's an easy job as you can access the battery door easily, and there's plenty of room in the keyfob if you leave the battery door off. Then you're still in a difficult place because you have to imagine up a "secret compartment" in which to store the keyfob. Aside from that, maybe a thick enough Mylar bag could eat the radio waves as necessary, or lead foil you would get at a hobby shop that sells RC airplanes and gliders. ~ dan ~
Thanks, these are some interesting suggestions. A question came to mind about the rolling security code issue. I am currently not using my spare fob, and have it in a drawer in the house. Since I am not using it and it is not being exposed to the Prius, will I eventually encounter problems with it because of this? And what is a Faraday cage anyway?
An Altoids tin will not work for storing a fob inside the Prius, but the Hershey's Cacao Reserve Truffles tin will. I don't know why. So you can try various containers to see what will work. You can send me the truffles.
Does this mean that the spare key fob I never use, which sits in a drawer, is by now useless? I don't remember reading in the owner's manual that the spare key fob has to be used occasionally!
Have not looked into the fob but I think if you could get a strong strip of plastic and insert it between battery contact and connector like they do in some things you buy to save batterys while they are in storage, you may have to use a screw driver to put it in but could activate it by just pulling the strip out. It however would no longer be water proof. Just a thought....
A Faraday Cage is any metal enclosure designed to block radio waves. See http://en.wikipedia.org/wiki/Faraday_cage . It's easy to simply pull the battery from the fob and place it into the dash slot if you need it. After all, it's an emergency situation. In two years, I've not given any thought to losing a fob or, say, falling into a swimming pool with it. My wife carries the other fob in her purse, so she's either with me or can be reached if something happens to mine.
On flat batteries, my understanding is there are Two systems in the Fob: remote lock/unlock, battery powered RFID ignition start, passive (Car powered) The first is just like every other key-less car alarm remote; it sends radio waves and the car interprets them and unlocks the car, or not as it chooses. This system uses rolling codes to slow down car thieves with sniffing gear. The second is used to detect the fob is in the slot (for the non-"smart-key" model), or in the drivers pocket when sitting on the seat / walking up to the car door / pushing the little "lock" button ("smart-key" model). Since it uses no battery, it won't go flat. Since the Fob doesn't transmit anything, a car thief can't sniff anything. Instead the Fob stores a unique serial number, and the car has a list (something like 2 masters and 4 slaves, or maybe just six in total) of "allowed" Fobs. The communication between the car and Fob can be as simple as a broadcast (cheap) or a challenge-response (more secure); and the whole thing is low power close proximity. It occurs to me; if you have two keys for an alarm, they could never be "in sync" (using codes from the same "allowed" window); so the car must have to track two patterns anyway. Otherwise, after a hundred (and twenty-seven/-eight) times you open / close a door with the first remote, your back up fob would be useless on every alarmed car.
I just tested this (just right now...went out into the cold, cold night just to get the answer to this). I took my spare fob which I haven't used since the first week I bought my car. It's been sitting in a drawer in my bedroom. My Prius has been started well over a 100 times since I purchased it in Feb. The spare fob started it up with no problem at all - SmartKey function and all. I would've been royally pissed if that had not been the case...
Thank you. This is what I would expect it ought to do. I was surprised by the earlier post suggesting it might not. Glad to hear that's not an issue after all.
