Ok so today I was detailing the inside of my car and I noticed that on the ash tray in the back there is a check engine light imprint on it anyone know why? Also on the drivers side the pillar between the front and back door there is a small button about 1/4 of the way up from the floor what does that do? Thanks!

 

on some earlier a4's the oBDII port was located there. the button is to turn the interior motion sensors on and off for the alarm.