I have a 2003 TL and the remote key will unlock the car and open the trunk, but it will not LOCK or set the alarm anymore. I can lock the entire car by inserting the key in to the door lock, but I cannot lock the car with just the remote. This is the same with both remotes that I have, so I think it's something with the car, not the remote.

Any ideas?

 

Well, after determining that there was a problem, checking the key fob again and again, checking the spare key fob again and again, and then after spending 20 minutes searching this forum to determine if anyone else had run into this problem, I decided to go back to my car and check if the lock switch inside the car was working. It was, and everything thing seemed to be functioning fine, except that I could not lock and set the alarm remotely.

I sat there in my car for a moment, and then noticed a little red slanty light on my dash control panel. Hey, that looks like a door ajar light! And it was! Apparently, the back door was ajar, which, apparently, prevents the car from locking remotely or setting the alarm.

I closed the door properly, and the fob worked. I'm back in business. It was all operator error.

False alarm!