What was found
ON APPROACH INTO PHL EN ROUTE FROM PHX RECEIVED BRAKE STEERING CONTROL UNIT (BSCU) FAULT CHANNEL NR 1; SYSTEM PREVIOUSLY WAS MEL'D IN SNA (MEL 32-42-03, COND. 1 "BSCU SYS NR 1 INOP"). DECLARED EMERGENCY AND LANDED WITHOUT EVENT, AIRCRAFT ABLE TO TAXI TO GATE. MAINTENANCE REMOVED AND REPLACED BSCU IAW AWA T/C R2A32301. VENDOR FUNCTIONAL TEST OF BSCU S/N 118 WAS UNABLE TO CONFIRM REASON FOR REMOVAL (NO FAULT FOUND). PERFORMED SERVICE BULLETIN C20216-32-3229, PART NUMBER CONVERTED TO C202163382D32. UNIT TESTED AND RETURNED TO SERVICE IAW CMM 32-47-27.