two priuses -- one key?

This has been asked before on PC (roughly a year ago). I believe the answer was no.

*EDIT* Well, maybe I spoke too soon. I just found this post suggesting that it is possible if both vehicles use the same fob model:
http://priuschat.com/index.php?showtopic=19819

And another thread:
http://priuschat.com/index.php?showtopic=11755

... And more debate:
http://priuschat.com/index.php?showtopic=11680

 

FWIW...I'm too lazy to search. But someone actaully posted that they had 2 Prii and were able to program their 4 fobs (2 from each) for both cars.

And heard it on the internet so it must be true.

 

Nope not possible. We already tried it. I talked to the Toyota Prius techs and they tried. They even contacted their Toyota HQ to do it. If there is a way let me know.

I think the problem is the way the car interfaces with the car and changes the coe for the next query. The fob would have to be especially setup to know it deals with two seperate cars. So you would have to modify the fob.

 

I would hope that this is not possible, because that means it's even easier to steal the Prius

 

Another reason why it may not be possible is the fact that there's a chance you will sell your car in the future. You probably won't get a buyer if you tell them that your other car shares the same keys, unless they want to buy both cars.

 

theoretically it can be done, but it's also a PITA in theory.

the gist of it is that while it may be remotely possible to get a fob to recognize 2 cars, by using a fob on 1 car you'd essentially be telling the fob to forget about the other car, and you'd have to go through some re-registration step that pretty much negates the smartkey use of the fob.

that is, if you get the fob to recognize both cars, which as i said is quite the remote possibility.

 

<div class='quotetop'>QUOTE(seasidetraveler @ Aug 29 2006, 04:54 PM) [snapback]311278[/snapback]</div>

No, that's not right. You have to program the car to recognize the fob, not the other way around. A would be thief wanting to steal your Prius with a new fob would have to load the Prius on a flatbed, take it to the dealer, and have them program the Prius to use their fob.

Tom

 

If I could get my Prius fob to unlock the front door on my house (or any other lock) I'd be a happy tinkerer.
And I don't really care if some other Prius key works, too, since it's just not going to actually happen that way.

 

sks computer is gonna cost a lot more than a couple hundred bucks.

 

We got so used to the SKS (also homelink garage door openers) that we do not carry keys around anymore. Even my office uses RF tags to get us into the offices and security vaults. Then one day the garage door spring broke. All the doors had deadbolts or bars on them since we only enter through the garage. Had to break open a window. I would definitely pay to have all my doors accept my SKS.

hhhmm. How about salvaging the SKS computer out of a wrecked Prius and hooking it up to your door?

 

With the '01 model I believe it would be possible. I don't think(?) the
key has a rolling code, just a transponder chip.You'd have to change
over the mechanical part of the ignition and the locks on one car to
match the other, so the keys would work mechanically. Then you'd
teach that car to accept the keys from the other, and get a few
more keys.

You'll want to study up on the key teaching technique before you decide
anything. If you need to turn the old key as part of teaching the new,
you'd have a point where you'd need to have the locksmith pull all the
pins from the ignition lock, so it will work mechanically (briefly) with both
keys. After that they'd put back in the pins so it only turned for the new key.


>seasidetraveler:

>I would hope that this is not possible, because that means
it's even easier to steal the Prius

You have to teach the car to accept the new key, and you need a
key it already knows before you can teach it about a new one.
If the thief already has a key that the car knows, well you're
out of luck anyhow.

 

<div class='quotetop'>QUOTE(100MPG @ Sep 1 2006, 01:38 PM) [snapback]312838[/snapback]</div>

ok. let's talk about this for a second. this isn't exactly going to get you anywhere.

sks works by rolling code, the computer is in sync with the key. a very basic description of how this works is:
when you start up, the car asks the key what the secret password is. the key gives the secret password, then after it's verified it asks what the secret password is going to be next time. the car answers with the next planned secret password, and they agree that the car will ask this password and the key will answer with this password next time you want to start the car. so if you were to take that key, with the agreed-upon secret password in its memory, to a different computer it will not have the password the different computer has in mind. a key will only remember one password.

does this make sense? buying another sks computer would just be a waste of money here.

 

It was my understanding that the computer remembered a certain number of previous passwords. This is because you could press the fob while out of range of the car, and that this would change the password the fob sends to the car. How the car and the fob resynchronize I don't know.

Actually DanMan32 and/or mrv knows much more about this and has talked about it previously.

I thought the conclusion was that you could get the car to recognize the master and also a slave fob (the new 2nd fob), but only if both fobs were of the same model. It is my understanding that 2004 to 2005 should work, but in 2006 the fob was changed. Prior to 2004 I don't know about.

 

I was asked to post about this... Not that I've personally tried, but I can point to other posts from others who have tried.

Yes, the NHW11 and the NHW20 both use a rolling ID-coded ignition key.

On the NHW11, the ignition is a traditional metal key that you twist to start. There is an ID chip in the key's head. The car has to be programmed to accept the ID of the key ahead of time. However, these keys can be purchased for less than $20, cut at your local hardware store or the like (<$5), and you can program your car to accept it yourself if you do the programming dance correctly. However, you must make sure that when you program a new key, that you have an existing MASTER key to start the process (or else you have to replace the car's security ECU, which last I checked was more than US$600). The US Classic Prius came with 2 master (black) keyfobs, a sub/valet key (metal key cannot open trunk, and is unable to start a new programming sequence), and also with 2 remote lock/unlock/panic keyfobs. There's a separate programming dance for the remote keyless entry.
http://autos.groups.yahoo.com/group/toyota...s/message/24377
http://www.coastaletech.com/carkeys.htm
http://www.coastaletech.com/keys.htm
http://www.coastaletech.com/transmitters.htm
So unless you have the same door/ignition keycut on both of your NHW11 Prius, there's no real way or point to programming 2 Prius to recognize the same key. (It's cheap enough to make copies.) The remote keyless entry fobs are a little more expensive... I don't know about the UK NHW11's key/remote duplication process, as they have the remote keyless entry buttons built into the blocky ID chip end of the metal key...

Now, with the NHW20 Prius, you have even more complexity... There's the metal emergency key that can open the driver's door, there's the remote keyless entry, the rolling-ID engine immobilizer, and also the Smart Entry/Smart Start (aka Smart Key System) RFID. Now, you have 3 things to program/teach the car to accept, and unfortunately you pretty much have to go to a dealer because the process requires a Toyota scantool to do the programming. (Make sure that your dealer does ALL of the functions at once.)

For the 2006 model year, the keyfobs have changed part numbers. The newer keyfobs (2006 onwards) can be programmed to all NHW20, but the older 2004-2005 keyfobs can only be programmed to 2004-2005 Prius. (For 2004-2005, there are different keyfobs for SE&SS and non-smart, which you can tell the difference by the color of the Toyota logo.) I know that the engine immobilizer function can definitely be programmed for 2 Prius to recognize the same key, but most reports are that the remote keyless entry functions will not work. I don't recall which way about the Smart functions. There have definitely been issues with eBay purchased used keyfobs not wanting to program all functions (such as remote keyless entry).
http://autos.groups.yahoo.com/group/Prius-2G/message/53443
http://autos.groups.yahoo.com/group/Prius-2G/message/50912

On a NHW11 Prius, you can program up to 4 remotes, 4 master keys, 2 sub/valet keys. If you lose your last master key, you cannot start over and must replace the security ECU...

On a NHW20 Prius, all keys are master keys. My understanding is that there is a way to re-initialize the security ECU on the NHW20 Prius using the dealer's scantool, although some dealers appear to go the more expensive/less labor intensive route of replacing the security ECU. I know I've seen a post by DanMan on www.priusonline.com about this, but I cannot find the link at the moment... I think you can program up to 4 keyfobs to be registered to a car, and I do know of some dual 2004/2005 owners that have the same 4 keyfobs programmed to each car.

Don't worry about selling one of the two cars, and having the other person concerned that you still have the keys... Besides the procedure to add a new key, there is also the procedure to delete all known keys (other than the one that started the process), so you can remove all the keys and then re-add just the ones for the car that you're selling. (Also a good idea if you lose a key, that you do the delete all and add all your existing keys back, as you don't want someone finding your key and stealing your car (a stolen keyfob has been reported at least once as a method of successfully stealing a Prius).)

Did I forget anything?

 

<div class='quotetop'>QUOTE(submarining @ Oct 1 2006, 11:35 PM) [snapback]326711[/snapback]</div>

Most rolling code systems use a resynchronization method that requires the user to press the fob button several times within range of the receiver. Without going into too much technical detail, what happens is after rejecting the first couple of pushes, the receiver realizes the lack of synchronization and attempts to find the proper place in the rolling code. If it's the right fob, the receiver can find the code pattern and sync up. The beauty of this resynchronization method is that it plays into normal human behavior: if your first push of the fob button doesn't unlock your car, what do you normally do? Push it again. It's what we always do. You end up thinking "I must have been out of range on that first push."

To avoid excessive use of resynchronization, the receiver allows a certain number of key codes adjacent to the expected one before rejecting the code. Say, for example, the receiver is set to allow any of the next five codes before rejecting. You could accidentally press your fob button up to four times before returning to your car and still have it unlock without resynchronizing. Allowing more code numbers reduces the chances of having to do resynchronization, but lowers the security of the lock.

Tom

 

DH has yet to play around with this to see what happens. he's kinda caught up in the pre-holiday-travel busy maintenance season, and we've got a lot of other things going on lately so this isn't nearly on our top list of priorities.

basically he's going to try everything he can to see what he can get to work and how to do so, and what simply will not work.

don't hold us to doing this any time soon though.

mrv, i posted the info for the immobilizer reset on priusonline so both boards have it.

 

I don't believe the unpowered RFID, that would be the key with the classic Prius and the new Prius fob when put into the slot, is rolling code. But it might, I am not sure. Seems like a lot of power for a short burst of energy from a tiny coil to be able to do all that work.
But the remote functions of the fob, including SKS, is rolling code. If the next code is missed, such as pressing the button on the fob while out of range, the car will look ahead for up to about 250 codes. If any of those match, the fob is accepted. If you have pressed the fob buttons more than that out of range, then you're out of luck with the remote functions, but you can still put the fob in the slot.

Now I always thought that the communications from the fob to the car was one way, and that the oscillator was simply a trigger, a tap on the shoulder if you will, for the fob to send an authentication code. Someone suggested that the oscillator sends a pre-code, which the fob uses to generate a response in combination with the next rolling code. This is known as a 3 way handshake, and is used when you log onto a dialup account for internet access. I tend to disagree with this thought, but I can't dismiss it either. This might prevent SKS from working across two cars.

But in theory, a fob should be able to be programmed to work between two cars, assuming everything is electrically the same: same freqencies, same code algorithms. One way to know that this should be the case is if the part number for the fob in both cars is the same. Now it is possible that production changes were made where a fob could be downward compatable, but not upward, or vice versa. One change that had been made was to avoid interference with Mobile's SpeedPass. I believe the triggering oscillators were replaced. So a new fob could accept either oscillator frequency, the old or the new, but the older fob would only know about the old oscillator frequency.

I know dealers have a great deal of time programming SKS, remote door lock, and the immobilizer transponder even with new fobs, so if a fob can't be paired completely between 2 cars, it could be the error of the dealer.

There's no danger of security to pair fobs across two cars, even if you sell one car. For the purchaser's sake and for yours, you'd want to have the cars reprogrammed to no longer accept the other car's fob. Otherwise the purchaser could get into your other car, and you into what is now his. This is also true about the homelink. Be sure to clear it if you sell your car, so they can't get into your home with it.