Buttons on AT

Alright there is this little button on the shift plate for the automatic 2000 s40 1.9T that looks like a W. I was wondering what this was for because as far as my understanding goes the overdrive is a button on the actual shifter just below the release knob. any information is helpful :) merry christmas and happy holidays!

The small "w" button on the right side of the AT shifter in an AT-equipped s40 is for the "winter driving mode". When you push the button a large orange arrow should appear in the lower right corner of the instrument panel indication the car is in winter mode. Winter mode will also be activated automatically when you use any of the lower gears (anything past D on your shifter). Winter mode uses the ECU and engine management to effectively lessen the amount of torque going to the wheels. So if you are sitting at a light and floor it, instead of the turbo spooling up and the car snapping you into the seat, you will accelerate as if you eased onto the throttle. This is to prevent wheelspin in wet or wintery conditions.