Key fobs and safety question

Hi Wavey,
Yes on the first paragraph if you don't want to take the FOB with you. Wrap the FOB and hide it, take out the mechanical key, lock the doors.

On the second part, if you doors are locked (in drive) they will not open if someone on the outside tried to open it. Two different signal areas (SKS and Engine Immobilizer).

Peter

 

Through multiple senors, one in each front doors, one in the hatch, 2-3 inside the cabin, the ECU can compute based on signal strength from all sensors and triangulate the location of the fob. Once it is determined that the fob is in the cabin, you are allowed to start the engine, and no one will be allowed to unlock the door from outside.
The best way to appreciate the system is to try it yourself.

 

The security computer tracks where the keyfob is located, and whether or not the ignition is turned on. The door handle sensor is only activated when the ignition is off, the doors are locked, and the proper keyfob is sensed within about 3 feet of the door.

Once the door is unlocked, the detection moves to inside the car. If the keyfob is detected inside the car, then the Power button is enabled. When the ignition is ON, the keyfob detection is turned OFF.

There are a number of ways in which the locking system can be configured. I think it's section 6-2 of the 2010 owner's manual that describes all of the options. Things like do you want all the doors to unlock with a single press of the keyfob key, or should it require two presses.

It takes a while to understand all of the intricacies of the security system. As an example, my wife and I got into the car at about the same time. I had unlocked both doors with my mechanical key, and was going to use the dumb keyfob that I keep inside the car. But since my wife had her smart keyfob with her, I could start the car based on her keyfob. Later when we both approached the car from opposite sides, I just assumed that her keyfob near the passenger door would allow me to open the driver's side door (I only had a mechanical key on me). No way - she had to touch the passenger door handle, which unlocked all of the doors. But then, that's just the way my car is configured. It probably could be configured so that only the door near the keyfob would be unlocked.

To answer the next question, I have a way of losing keys. So rather than risk a several hundred dollar keyfob when I go trail running, I just carry a mechanical key that locks/unlocks the doors. I leave a dumb keyfob inside the car, which allows me to start the car. The dumb keyfob (an ordinary one with the battery removed) is not detected by the security system except when it's inserted in the dash (Gen2 car - just hold the keyfob next to the power button on a Gen3 car). When I lose a mechanical key, I just get another one instead of having to replace the entire keyfob.

 

I don't think the system uses triangulation to locate a keyfob. There is only one receiver on the car to detect a keyfob transmission. There are oscillators (output only, 134.2 kHz) at each detection point (outside driver door, outside passenger door, outside trunk, inside car, and inside trunk). My guess is that the oscillators either each send a unique signal, or perhaps their transmissions are staggered. The keyfob responds to the nearest oscillator, and may include the identification of the oscillator that it heard in the reply.

I suppose you could scope the signals to several of the oscillators and see if they use staggered transmission and/or different messages. I think the oscillators broadcast a message like "this is car number xxx, location y". Then the keyfob replies "this is keyfob zzz responding to location y". If the keyfob doesn't recognize the car number, then it doesn't reply.

 

I just didn't feel comfortable leaving the FOB in the car when I go running. I picked up one of these and the FOB fits perfectly.
Nike Running Shoe Wallet at REI.com

 

I've been running for over 30 years. I'd never attach anything (especially car keys) to my shoes. You wouldn't believe how many runners have lost their car keys doing this.

The most effective method for avoiding losing your keys is to clip them to your shorts.

Good Luck,

Keith

 

RobH,
"Triangulation" is easier for layman to understand. That was my intention.
In fact, assuming Prius' system is similar to my CX9's, each sensor generates pulses of certain pre-set frequency. When the fob is within range, the frequency changes depending on the signal strength. By comparing the frequencies of each sensors, the ECU can "see" where the fob is. Those sensors are based on oscillators as you mentioned. There is indeed only one receiver whose antenna is near the ECU. Its coverage is about 15ft-20ft. The effective range of sensors is only 3ft.

 

When I go running I always carry a water bottle attached to a belt. I keep the key fob in the pocket of the water belt.

 

That's what I used to do with my 4Runner key and still do with my wife's Civic key when we take her car. BUT, salty sweat is not good for electronic equipment and I don't want to soak my FOB in sweat (yes I sweat that much after an hour of running).

When I first got the little shoe wallet I didn't like how it had a clip on the back to slide under the shoe laces so I poked a hole in it and tied a little cord to prevent the clip from slipping out of the laces. I use this on a dedicated pair of running shoes so it never comes off until it's time for a new pair of shoes. The velcro is pretty strong but if you were really worried you could just safety pin the FOB to the lip of the shoe wallet that way if the lip came open for some reason AND the FOB worked it's way out, it wouldn't go anywhere. Or, you could safety pin the lip closed. The little shoe wallet is convenient, safe, and I'm not worried about sweat ruining my FOB.