Wanna hear a good one? Q5 key starts X3?
 

Here's a funny one for you. The other day I took my wife's Q5 into town & got a call from her. She too had gone into town and taken my X3. She called me to say she could not restart my X3 after her first stop in town. She could not understand why? She noted that she had taken her Q5 key instead of her key to my X3. How did she manage to start my X3 with her Q5 key you may be asking? Here's the answer. Our keys hang just inside our house at the door to the garage. She put the wrong key in her pocket & because the X3 key was within proximity of the X3, the vehicle started & she drove away. She obviously could not restart the X3 because she had her Q5 key. (No Blonde Jokes Please) Lesson learned.

Ouch. Proximity keys can be a nightmare...

Good to know! We are buying a house where we will have a little table right near the garage door for our keys, purse, etc. Your experience will definitely come in handy and just might save myself or my wife an embarrassing situation. :-)

That can happen even without proximity keys...

At the time we had a Q5 and an A4. On my way to work got a phone call, "I can not start the car...". Turned around just to show that although the two keys look the same they can not start both cars. No, the Q5 key can not start the A4...


.

Doesn't the Q5 key have to be inside the car to start it?

Something must be wrong with your X3 because this just does not sound right, or at least not how BMW intended for it to work. The keyless start/stop/unlock/lock systems in cars require much closer proximity than you describe is happening to your X3. I've had a bunch of cars with such a system and they've all worked this way, including 2 BMWs (2006 M5 and 2008 M3). In both of those cars, I could not unlock a door unless the key was within about 3 feet of that respective door. Even if I rested the key on the rear trunk lid, it wouldn't let me unlock the front door by grabbing the handle. And with starting the engine, they simply would not start if the key was not inside the car. Even if I put the key on the roof or on a bench just outside the driver's side door, it wouldn't start. This worked the same for several Mercedes, VW, and Audis I've had the last few years. And I tested the proximity functionality for each of them for fear that such a thing would happen to me (park the car outside and someone unauthorized being able to get in and start it because the key fob proximity was too sensitive).

I had something weird happen the other day. I was driving with my fob in my pocket and then the HUD beeped at me and displayed "is the key in the car?" I then put the fob into the slot and it went away. I was wondering what would have happened if I didn't do anything? I was thinking the car might turn off if it didn't detect the key. That appears to not be the case.

How old is the battery in your FOB?

I took delivery of a 2013 in May. So not that old.