carlinux
the temp display maybe/probably is in the meter panel and not the Nav. The spped mph/kph may also be determined by the meter panel. I know that if you disconnect the speed sense
signal to the nav , the line that goes between the meter panel and the nav unit the speedometer still works fine.

One thing that seemed strange if you disconnect the RX line on the nav board the display goes white and displays the trip and OD as 0 km.

Not sure if any of this helps but thought I would put it out there.