Bosch GS8.87 Transmission Management

DTC P1602
CAN Message N_MOT invalid (FFFFh).

Possible causes:
- Engine speed measurement fault present in engine management ECM.

Engine speed measurement fault present in engine management ECM.
CHECK THE FOLLOWING:
- Read ECM fault codes and diagnose any faults likely to cause problems with engine speed measurement (e.g. Crankshaft sensor, reference position).
POSSIBLE FAULTS
- Fault codes set in engine management ECM.