one FOB two Prii

I don't think so. The fobs use a rolling code which will get out of sync if they are used with another car. I can't say no for sure, but I find the odds unlikely.

Tom

 

We also have Two Prius (or Prii) Mine is a magnetic grey 08 and oh so pretty ( only two weeks old ! YEY ) my husband has seaside pearl 08. I also have 2 fobs ( not smart key ) but I often wished they could have colored rubber covers like on some ipods or phones to differentiate between the two !

 

This issue of using one keyfob for multiple cars has come up several times before. I think it would work if you could actually add a used keyfob to a different car. But many people have found that their car cannot add a used keyfob. Sometimes it works, but many other times it doesn't.

What definitely can be done is to program both cars for all of the keyfob transponders. So a particular keyfob will have full smart function on one car, and keyslot function on both cars.

The standard mechanical keys are only going to function on the specific car that they're designed for. But note that the actual lock only uses one side of the two sided key. You could have a key custom cut with the code for one car on one side, and a different cut for another car on the other side. If the key doesn't work on a particular car, you turn it over to use the other cut.

Another idea for the mechanical key is to carry an ordinary $2 copy made at the local hardware store.

So it is possible to have one keyfob that works on two cars. The smart function works on only one car. The keyslot function works on both cars. A custom mechanical key with two different cuts works on both cars, but you have to invert the key between the two cars.

 

The key system in the car can track four separate fobs. Each fob can track only one car. You need a fob with multiple codes, essentially two fobs in one.

Tom

 

There are 4 locking systems in the keyfob. They are the mechanical key, the transponder, the remote (button press), and the proximity functions.

The mechanical key is cut the same way on both edges, but the door lock only uses one edge. So you could actually have different cuts on the two edges, and each cut would work with a different car. You can make any number of copies of the mechanical key, as they will all appear exactly the same to the lock.

The transponder is a short range system (about an inch). It is used when you plug the keyfob into the keyslot on the dash. I don't believe there is any changeable memory in the transponder, so it doesn't rotate its code. It is some sort of challenge/response function that may or may not vary between usages. If it does vary, it's a fairly simple algorithm since many similar transponders can be duplicated by a locksmith. A transponder ID code is registered by the Transponder Key ECU (a computer in the car). So it is the car that recognizes a transponder, not the transponder that recognizes the car. The car can register a maximum of 5 different transponders.

The remote (button press) system is a one way system that works up to about 30 feet. The remote probably rotates the code that it sends, and the car understands the rotation sequence. There has been considerable discussion about how many different codes are used, and what would happen if you, for example, pressed a button too many times while out of range of the car. So the theory is that there is a rotation window that both the remote and the car must keep in synchronization. If the transmission does vary, then simply replaying a recorded transmission would not work. Because of the rotating sequence, using a single remote with multiple cars would seem to run the risk of getting out of synchronization with the car not being used. Each car can register a maximum of 5 different remotes.

The proximity function is the really slick system we generally call SKS or Smart. It probably uses the same ID code as the remote. But independent of the ID code, there is also a changing encryption process that renders this code quite secure. Transmitters at the front doors, the trunk, and the console between the seats regularly poll for the presence of a keyfob. A keyfob within about 30 inches from a transmitter responds with its ID code. If the Certification ECU computer accepts the encrypted ID code, then the system enables the door unlock or Power button, depending upon where the keyfob is detected. The proximity registration data is the same as is used by the remote. The limit of 5 different keyfobs applies.

Registration of the transponder and the remote/proximity functions are two separate processes. While they are generally thought of as single process, there is nothing technical requiring that they be synchronized. A car could have 2 remotes and 4 transponders registered. The extra transponders could be the ones in the keyfobs for another car.

 

I think that this is yet another example of where the low-tech duct tape solution would work best.

 

just put a small dot shaped color sticker blue, green, red, or whatever color your Prius' are on each FOB right next to the Toyota emblem. Easy solution.