Hi, recoding will fix it.

To confirm that the nav is functional, watch the red power light on the nav.
Exit the car, turn key off, shut all doors but leave boot open.
Observe red LED on nav. it will blink, and after 60 seconds, will blink rapidly, then go out.

Then use your key to unlock the car, or open a door. Look back at the nav. Has the red LED come back on?
If so, then the nav has recognised and responded to the 'wake up' message on the databus.

If the nav powers down and wakes up OK, then this indicates the nav CPU is working fine, and the databus interface is fine.

If the red LED glows steady and never blinks, the nav main board is faulty.

If you have confirmed the CPU is OK, remove the nav and look for a label with a chassis number on it. Often the nav coding is printed on this label BMWC01S = colour, BMWM01S = monochrome

If CPU is OK and nav is coded for mono, then a recode will fix it.

Jochen