What was found
DURING TAXI AFTER LANDING, AIRCRAFT STARTED TO TURN LEFT WITHOUT INPUT TO TILLER OR RUDDER PEDALS. AIRCRAFT EXAMINED AND NO APPARENT CAUSE WAS IDENTIFIED. CONTACTED CESSNA AND REQUESTED A REPLACEMENT STEERING UNIT. TECHNICIANS FOR ICT AND LGB CAME TO PHX AND CHANGED OUT UNIT. JACKED AIRCRAFT AND PERFORMED RIGGING AND OPERATIONAL CHECKS. AIRCRAFT TAXI CHECKED AND FUNCTIONAL CHECK FLIGHT PERFORMED. TC: 119.