Use your cell phone to unlock car..

A Cell phone transmits audio information received by its microphone or digital information from its own keypad or attached digital device. There is no data path for the fob's stream of digital information. Furthermore, even if the fob's data were transmitted to another cell phone, there is no compatible modulation system for interacting with the car.

Could a cell phone be designed to do this? Yes. Do existing cell phones work this way? No.

Tom

 

My your just full of mis-information arn't you. Sure electronics can emit Spurious Emissions, (The Tech Term) but thats were the FCC steps in and mandates just what level of those emissions are. Thats why the interior of most electrical devices that can generate S.E. are shielded by the case of the item in question. A RF deadening agent is sprayed on the inside of the case to prevent or suppress leakage of these signals.

When the KeyFob does not work and you have a cell next to it it's the RF from the cell transmitter overloading the "Front End" of the SKS receiver and preventing the signal from being heard. This is a common thing, it does not just apply to Prius FOB's.

The type of cell sevice does not matter, TDMA, CDMA, GSM, TD-CDMA, until a interface is created to link the FOB's data burst to the cell phones system, and a interface is created from the cell phone to SKS receiver, this just Ain't gonna work!!!

Don't bother Sandman, the whole purpose of the SKS FOB is to broadcast a UNIQUE RF ID to a single receiver. You will not get FOB A from Prius A to work on Prius B. Unless Prius B is set up to recognise FOB A's databurst!

Another Myth busted, one at a time!!

73 de Pat KK6PD

 

It does work. I was just able to unlock the car door of Obama's half brother in Kenya!

 

No workee, no way, no how!

 

The data path that I'm proposing is RFI, or electrical noise. Just look at the number of people who report that you shouldn't put your cell phone in the same pocket as your keyfob. The devices interact, and not in any intended way. Usually the interaction is destructive - the keyfob signal gets trashed by the cellphone signal. But it is entirely plausible that a cellphone could pick up the keyfob signal as electrical noise.

It's a long path from plausible to demonstrated, so I'm not claiming that this scheme works. But I don't dismiss it out of hand.

On the other hand, a bumpkey is a much simpler solution to a lockout.

 

The FOB is RF. It doesn't work via sound like an analog phone dialing .... using differing pitched sounds. So, I would guess that there is NO WAY this can possibly work.

... Brad

 

I'm not dismissing it out of hand. I'm an electrical engineer with a lot of training and experience in RF and digital design. It's my studied opinion that this urban myth is just that.

I won't bother to restate all of the reasons. See KK6PD's post for those.

Tom

 

I've got a related question about the keyfob and the SKS system:
Does the Prius SKS system trigger the keyfob to transmit its RF ID unlock code only when it's near the doors or hatch?
I assume that's how it works since the keyfob battery would go dead in a short time if it were transmitting the RF ID code continuously.
Also, if true, this would make the keyfob a transceiver and it might be possible for a thief to acquire your unlock code, without your knowledge, using an RF device.

 

Yes, this is how it works. The key fob listens quietly until it hears a query from the car, then responds with the proper code. This is why storing the fob near an RF source can drain the fob battery. A strong RF signal can fool the fob into replying repeatedly.

This is also true. A smart thief with a transceiver could force your fob to reply repeatedly and capture code information. Since a private key and rolling code are used, it would take a large number of cycles to compromise security. It's theoretically possible, but not very practical. A flatbed truck is easier, or just steal your fob.

Tom

 

When I read the original post, I knew it would not work as described. I kept reading through all the posts, however, and, as usual on this forum, I learned something useful (the FOB is actually a transceiver and it's battery can be drained if stored near an RF source!) Thanks.

 

Here is another useful tidbit: storing the fob near the car can drain the 12V battery on the Prius. The SKS is one of the persistent battery drains on the battery even when the car is off. That's because the SKS has to send out a beacon signal, asking any fob in the area to please respond. This is why the manual and many posters recommend that the SKS be disabled if the car is parked for an extended period, such as a couple of weeks at the airport. You use the little SKS button below the steering wheel to do this.

As for storing the fob near the car (within about 30 feet), when you do this, the fob responds every time it hears the beacon signal. This means the car and fob spend a lot of time and energy talking to each other, burning up the batteries in both.

Newer Prius have a feature that automatically disables the SKS after a period of time, preventing the car battery from being discharged. When this feature engages, you have to manually push the unlock button on the fob to get in the car. After that, everything goes back to normal. Still, it's better to not rely on the automatic shutoff.

Tom

 

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