I thought I read somewhere there was a 'service' menu on the GM nav units?

Was I mistaken? I searched for it, but I can't find it.

something about pressing the bottom left on a blue screen somewhere?

thanks.

 

An old post for an '05 said when in the NAV map mode, press and release NAV RPT, then press and hold CONFIG until the NAVIGATION CHECK menu pops up (about 12-15 seconds). Hit the calibration button and follow the directions.

Don't know if it'll work on the NBS.