It's not a "sensor" - it's a microswitch at the bottom of the GPS/Navigation carriage that's obviously not fully activating or has a loose connector.
Remove the windshield and then four screws to lift the GPS carriage to access the microswitch.
See the part in the below eBay ad.
Support GPS BMW K 1600 Gt/Gtl | eBay
Remove the windshield and then four screws to lift the GPS carriage to access the microswitch.
See the part in the below eBay ad.
Support GPS BMW K 1600 Gt/Gtl | eBay
02 | 61 31 7 671 111 | MICROSWITCH | 9.74 | 1 | $29.18 |