If you have command you can get the GPS to show you it's idea of your speed, switch on the car with the Radio on press the following at the same time
Mute button
+ button
1 button
3 button
Hold for 5 seconds, then the diagnostic menus come up ,
then the diagnostic menus come up , go into "Versions" ,
scroll through till you get to "infos" the one that shows you GPS position, it also shows mph.
When compared to the speedo speed this reading lags and only catches up when doing a constant speed, even still it will occasionally over or under read, speedo appears more accurate.
Other hings can be accessed including errors logs etc.
Mute button
+ button
1 button
3 button
Hold for 5 seconds, then the diagnostic menus come up ,
then the diagnostic menus come up , go into "Versions" ,
scroll through till you get to "infos" the one that shows you GPS position, it also shows mph.
When compared to the speedo speed this reading lags and only catches up when doing a constant speed, even still it will occasionally over or under read, speedo appears more accurate.
Other hings can be accessed including errors logs etc.
