Read the etacs tweaks thread. Or in short version :
1. Buy any j2534 tools (i recommend
mini vci, cheap)
2. Download etacsdecoder software.
3. Install j2534 driver on your laptop. Make sure it was installed correctly.
4. Fire up etacsdecoder software. Choose j2534 from the settings menu.
5. Connect the j2534 tools to the laptop and the obd2 connector on the car.
6. Slide on the etacsdecoder tools, make sure key was on (engine not started). It will read and display all the etacs setup pf your car.
7. Change ambient temperature from not available to available on etacs variant page. Press decode (make sure you are connected to internet). Then press write to car. Follow what the software tell you to.
8. After cycle the ign, enjoy the changes you've made.
Further info, see the software site.