I lock car using key fob, get chirps & alarm is set.
Done this thousands of times.
Recently my car is parked in my driveway instead of in the garage.
Next day, I go to car & notice the driver door button is up/unlock position.
I open door & alarm goes off!
How is this possible?

I thought only 2 options; doors locked & alarm on or door unlocked & alarm off.
How could the alarm have been on while the driver door was unlocked?

 

Quick question does the driver door still lock with key fob or has the actuator failed? I had an XJ8 where the driver door only unlocked/locked with the physical key and the alarm could be set off even when unlocked. Other possibility could be a sensor failure in the door making it unable to tell the door is locked but I would just disconnect the negative battery lead for a few hours to reset the system and see if the issue pops up again. If none of this applies or helps your alarm module may be failing/bugging out and I would have a shop run diagnostics.

 

Happened to me before I bought mine! Saw it at the dealership on the way home one night, and stopped to look. Oh look, driver's door is unlocked. Open, and then chirp...chirp....chirpchirpchirp... well no sense sticking around for the cops to ask what I'm doing at eleven at night on a dealership "breaking" into a Jag!

In my case, the actuator has gone wonky, so there are times it does work, times it doesn't. In most cases though, I can lock the car with the remote and then lock the driver's door with the key, just so all four doors are secure.

 

True it was a constant source of embarrassment especially if you grab something out of your car late at night and you can't get to your key fob or put the key in the ignition fast enough! I once had a roommate move my XJ8 with the sticking actuator for street sweeping while I was on a business trip and after opening the sunroof and all windows by holding the key too long they set off the alarm. After that they refused to touch the car.