A B767 FLT CREW GETS A LAST MINUTE RWY CHANGE ON THE SEAVU ARRIVAL TO LAX AND DEVIATES FROM THE CLEARED TRACK.

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ORIGINALLY CLRED TO FLY THE SEAVU ARR RWY 25L AT LAX. AFTER BEGINNING THE ARR; APCH CHANGED OUR ARR TO THE SEAVU RWY 24R. I HAD PRELOADED THE SEAVU RWY 24R IN RTE 2 AND UPON CLRNC EXECUTED RTE 2. THE INITIAL POINTS ALL MATCHED. HOWEVER; WHILE ON THE ARR; I REALIZED NOT ALL THE POINTS MATCHED AND BEGAN INVESTIGATING. ALMOST IMMEDIATELY AFTER; THE ACFT TURNED EARLIER THAN IT SHOULD HAVE ON THE SEAVU AND I REALIZED THAT I HAD MOST LIKELY INADVERTENTLY EXECUTED THE WRONG ARR OR POSSIBLY; THE FMS DATABASE WAS NOT CORRECT. AT THE SAME EXACT TIME; APCH CTL INQUIRED ABOUT OUR ARRIVAL. I REQUESTED A VECTOR UNTIL WE COULD CORRECT THE DISCREPANCY. APCH CTL ISSUED A VECTOR AND ALT TO DSND TO. THEN APCH ISSUED A CLRNC TO PALAC AND TO INTERCEPT THE RWY 24R ILS. WE COMPLIED. APCH MADE NO OTHER INQUIRIES ABOUT THE EVENT. THERE WERE NO CONFLICTS AND NO OTHER ACTION WAS NECESSARY. AT THE SAME TIME AS THE EVENTS DESCRIBED ABOVE; MY FO AND MYSELF WERE EVALUATING A MINOR ENG MALFUNCTION THAT HAD PREVIOUSLY BEEN RPTED AND WHICH WE BEGAN EXPERIENCING IMMEDIATELY UPON DSCNT INTO LAX.