What was found
(CAN) ON TAXI OUT TO RUNWAY, THE CREW LOST THE CONTROL OF THE NOSE WHEEL STEERING. MAINTENANCE WAS UNABLE TO REPAIR THE PROBLEM WITHOUT BRINGING THE ACFT BACK TO A GATE. THE ACFT WAS TOWED BACK TO A GATE TO BE REPAIRED. TSM 32-42-00-810-929-A CARRIED WITH NO FAULT. ACFT TAXING IN AND OUT APRON 2 TIME NO FAULT. BSCU (UAL POOL PART) REPLACED AND TESTED SERVICEABLE, WITH ACFT TAXING IN APRON, IAW AMM 32-42-34, PB 401.