During the 2002 and 2003 model years both Olds Alero and Olds Aurora used a keyless entry system paired with a 4-button remote transmitter that has FCC ID KOBLEAR1XT on the back of the case. The vehicles may or may not have had seat memory. If they did, the original keyfobs had fob number “1” or “2” on the back of the case to differentiate them. (These numbers are purely cosmetic, the transmitters are identical except for the case marking.) Remotes Unlimited sells a replacement remote with part number 512-1512 that works for these systems. See it at this link.
While the keyless entry systems in many GM vehicles that use part 512-1512 can be programmed by the user to accept a replacement remote, Oldsmobile chose to make these vehicles only programmable with a special “scan” tool. So you will have to take the new remote and your vehicle to a dealership for programming.
Pep Boys sells this remote in all of its stores as part number CPR-8512. You can buy it there at a price well below the GM dealership price.