My parents asked me:

If they start the car, and remove the magnetic key from the car from a distance, will the car continue to act as though the magnetic key is still there or will it shut off after some time?

 

it will not shut off as far as i know. ive gone 10 minutes away from car with it shutting off

 

It does not shut off. It does this so if your fob battery dies while you are driving, it doesn't shut off, putting you in a potentially dangerous situation (like the car stalling on the highway or in an intersection).

 

You mean "...with it NOT shutting off.", right?

 

There will be a reminder on the dash telling the driver that the key is not detected.
I did an experiment a few years back, and im sure it still holds true today.
I drove 15 miles one way without the key fob, and the RX just keep on going, i know i can go farther but i have decided to return home.

 

I was also curious about this and your answer makes a lot of sense.

 

I always assumed the "Vehicle theft-deterrent and engine-immobilizer system" mentioned in http://www.lexus.com/models/RX/safety works by not detecting the key if someone attempts to carjack the vehicle or drive away if you leave the engine running and go inside the house to grab something you forgot.

So what exactly is "Vehicle theft-deterrent and engine-immobilizer system"? How does it work? I see a blinking red light but have never heard any alarm go off - I would think over the last 1 year, I would have set off the alarm accidentally if there was one that gets armed whenever I lock the vehicle. I have a 2013 RX350.

 

being slightly hard of hearing I once went shooting and left the car on for almost an hour...I now have hearing aids and can actually heard the BEEP when exiting the car while running with the fob in my pocket....

 

Try this: park your car in the driveway, roll down the windows, get out of the car, lock the car with your fob, take the fob into the house and leave it there, go back to the car and reach in the window and using the handle inside the car on the door, open the car door.

Oh, before trying this, read the manual about how to silence your car, it may be a bit noisy. At least the last time I tried this it was a bit loud.

 

Your vehicle features 2 anti-theft systems. One is the standard alarm and the other is engine immobilizer. The alarm will go off if someone unlocks the car (from the inside), opens any door, opens trunk door, or pops the hood. Obviously, this is not something you would do in a normal circumstance, therefore you never set it off. If you happen to open the car with the physical key, this also disengages the alarm and will not trigger it.
The alarm arms itself when you lock the vehicle using either the FOB, door handle, or the key.

Immobilizer is a different technology, not related to the alarm. It does exactly what it sounds like - immobilizes the vehicle until the key fob has been authenticated. It makes more sense in traditional mechanical keys. For example, mechanical keys have RFID chips built-in into them. If the key was simply copied and RFID was not programmed into the immobilizer, the car would crank till the cows come home, but the engine would not start. With the smart key, this functionality has been integrated. The code read from the smart key is used to enable engine starting. If the battery is the key fob dies, the RFID code can be read by holding the fob next to the start button.

Once the vehicle has been started, it will not turn itself off if the key is removed from the cabin.

 

Classic scenario involves the couple driving to the train station, peck on the cheek and the partner with the key hops on the 7:15 to the city. Homeward bound driver stops to shop ( substitute No-Tell Motel for R rated version) and guess what? No start when it's time to go home...