My wife has a 2006 X which has an intermittent Driver side door ajar warning. At that moment the Dome/vanity lights are all on. I assume it's
a stuck door sensor on the driver side. Where is the sensor? And are there any suggestions on a simple repair without taking the door apart?

 

The door sensor is in the locking mechanism. A rubber gromit sits
on top of it. When the door is closed the striker pin compresses the
sensor. They can get stuck. The use of WD 40 seems to have relieved the problem.