What was found
LANDED RWY 27, AFTER DECELERATING TO TAXI SPEED, NOSE STEERING DISCONNECTED AND AURAL WARNING SOUNDED. AIRCRAFT WAS STOPPED ON TAXIWAY. SYSTEM WOULD NOT REMAIN ARMED AND AIRCRAFT COULD NOT BE CONTROLLED WITH DIFFERENTIAL POWER AND BRAKING. ATC WAS NOTIFIED THAT A TUG WOULD BE REQUIRED TO CLEAR THE RWY AND PROCEED TO PARKING. AIRCRAFT WAS TOWED TO FBO FOR SERVICE.