AN MD11 WAS DISPATCHED IN NON COMPLIANCE WITH A TANK BOOST PUMP RELAY AND REMOTE CTL CIRCUIT BREAKER REPLACED IN AN INCORRECT TANK TO CLR A DEFERRED ITEM RESULTING IN A RETURN TO THE FIELD.

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ON AUG/XA/00; I RECEIVED TURNOVER FROM PREVIOUS SHIFT ON ACFT XYZ WORKING MCO. 'AUX LOWER R PUMP OFF' STATUS MESSAGE CAME ON DURING CLBOUT. PREVIOUS SHIFT TURNED OVER WIRING DIAGRAM MANUAL SCHEMATIC FOR THE FORWARD AUX TANKS. I MISUNDERSTOOD THAT THE STATUS MESSAGE ORIGINATED FROM THE FORWARD AUX TANK; WHEN IT ACTUALLY WAS FOR THE CTR AUX LOWER TANK. I PROCEEDED TO GATHER THE PREPULLED PARTS AND MAINT MANUAL FOR THE TASK OF REPLACING A REMOTE CTL CIRCUIT BREAKER AND CTL RELAY. I REMOVED PWR FROM THE ACFT; AND REPLACED REMOTE CTL CIRCUIT BREAKER B1 AND CTL RELAY R2. I REAPPLIED ACFT PWR; REACTIVATED THE AUX LOWER R PUMP THROUGH CENTRALIZED FAULT DISPLAY SYS AND PERFORMED A RETURN TO SVC TEST ON THE FUEL SYS CONTROLLER. THE SYS TEST PASSED; AND I REMOVED THE MCO AND PLACARD. THE MISUNDERSTANDING BTWN THE FUEL TANKS WAS UNINTENTIONAL AND COULD HAVE EASILY BEEN AVOIDED. THE NOMENCLATURE OF THE STATUS MESSAGE IS NOT SPECIFIC AND CONFUSING. IF THE STATUS MESSAGE SAID 'CTR AUX LOWER R PUMP;' I WOULD NOT HAVE LOOKED AT THE FORWARD AUX TANKS AT ALL. THE CTR AUX LOWER R PUMP DID NOT SHOW A HARD FAULT ON THE GND; ONLY DURING CLBOUT. IN THIS CASE; SINCE THE FUEL SYS RETURN TO SVC CHK PASSED; THERE WAS NO WAY FOR ME TO KNOW THAT I HAD CHANGED THE COMPONENTS FOR THE WRONG FUEL TANK. I HONESTLY DID NOT KNOW THAT THE CTR AUX UPPER AND LOWER FUEL TANKS EXISTED UNTIL TODAY