What was found
NOSE WHL STR INOP CAS: LOWERED L/G FOR LANDING AND GOT "STEER BY WIRE FAIL" CAS. COMPLETED QRH PROCEDURES AND MSG STILL ILLUMINATED. RAISED L/G AND DIVERTED TO AIRPORT WITH BIGGER RWY. LOWERED L/G AGAIN AND CAS DID NOT REAPPEAR. CONDUCTED NORMAL LANDING AND TAXI TO RAMP.
CORRECTIVE ACTION: PERFORMED FIM TASKS AS REQUESTED, EACH TASK WAS TROUBLESHOT DOWN TO REPLACE THE TILLER ASSEMBLY. REMOVED AND REPLACED TILLER ASSEMBLY WITH AN INSPECTED/TESTED UNIT. OPERATIONAL CHECKS GOOD. ALL WORK PERFORMED IAW GULFSTREAM G450 AMM 32-51-01 AND FIM TASKS 32503NWS1.