I don't think the car locks itself if any door was opened after it's unlocked. If you unlock the car without opening the doors, the car will lock itself after a certain period of time. If you leave the key inside the car, the car should not lock itself up. I've tried this a few times, if you put the key anywhere inside the car, when you try to lock the car by pressing the lock button on the door when it's open, the lock pops right back. If you take the key out, then you can lock the car by pressing the lock button then shut the door. I think it's designed to prevent the driver from locking himself/herself out. The only place where I can think of locking the key inside the car is the trunk, since it doesn't have a sensor inside the truck which pop the truck automatically if the key's inside.

 

I have been unable to do this. One time, my wife left her spare in the the car, and my key was in my pocket, and I pressed the door handle button, and it wouldn't lock and made a few short beeps (different from the door lock beep). I've also tried manually locking the doors with the interior door lock button, then shutting the door with the key in the car--it woudn't lock.

 

This is true. If the key is in the trunk, the cabin won't detect it.

 

A few people are saying that there is an auto lock feature that may cause the key to get locked in the car. I have yet to find either of these things to happen.

 

This is correct. When i brought my 350 in for the 1000 mile check up/key fob programming i asked about auto locking...answer...nope

but why not lexus if the fob isnt in the car it should lock once you reach a specified distance from the vehicle. just my .02

 

Now IS-F has this sensor. It is located near spare tire. Tried myself droping key deeply in the trunk and closed. It started blinking hazards and made some beep sounds..just needed to press trunk open button and it oppened.

 

That's not what I meant. I closed the key in the trunk of my IS 250, and when I hit the trunk lid button, it opened.

But--put the key in the trunk, and get in the car and try to start it--no go.

 

Apparently BMW has a problem with their 2006 and I don't know what else models where if you leave someone in the car without a key and lock it, they cannot get out even in an emergency! I asked Lexus if this was possible in the IS and they said no. I don't know about keys in the trunk!

 

Just don't be forgetful or careless then you will not have an issue... there is no real reason why you need to take out your key anyways with the push start and such...

 

If you put the key fob in the trunk and close it, you can open it by pressing the trunk button. IS250/350

 

so at least in Europe, they added new sensor in the trunk near spare tire. Or if some Europiens will reply that they have such, it means it is some regional modification...

 

for me, if i press unlcok on the key fob, or grab the handel with the keyfob in my pocket, and then DONT open the drivers side door and just wait about a minute, it will relock, i guess thtas so if you by accidently unlock while walking away and don't open the doors it knows your gone so locks it, but one time i unlocked the car and popped the trunk, opened the back door and put the keys on the rear driver side seat, and closed the door. I then took off my football pads and put them in my trunk, and as i was untying my cleats i heard the car beep and lock the car, leaving my keys in the back seat. I've also done this before while washing my car, but i have the spare at the house so thats no big deal