Assuming it is a Toyota remote system and not added:
1. Start with the key out of the ignition, drivers door is open all others closed and
drivers door is unlocked.
2. Perform these steps within 5 seconds.
A. Insert the key into the ignition(Do NOT Turn) Pull key out.
B. Insert the key into the ignition(Do NOT Turn) Pull key out.
3. Perform these steps within 40 seconds.
A. Close then open the drivers door.
B. Close then open the drivers door.
C. Insert the key into the ignition(Do NOT Turn) Pull key out.
4. Perform these steps within 40 seconds.
A. Close then open the drivers door.
B. Close then open the drivers door.
C. Insert the key into ignition and leave it in ignition.
D. Close the drivers door.
E. Turn the ignition to ON (Do NOT Start) then back to OFF.
F. Remove the key from the ignition.
5. Within 3 seconds, the power door locks should lock then unlock automatically
indicating successful entry into programming mode.
Return to step 1 if the locks do not cycle at this point.
6. Perform these steps within 40 seconds.
A. Press the lock and unlock buttons on the remtoe simutaneously for 1.5 seconds.
B. Immediately after letting go of the lock and unlock buttons,
Press the lock button by itself and hold for 2 seconds. Within 3 seconds, the door
locks should lock and then unlock once indicating successful programming. If
the door locks cycle twice, repeat steps A and B in step 6 as the remote was
not accepted.
C. Repeat steps A and B in step 6 for each new remote.
7. Open drivers door.
This info came from http://www.programyourremote.com. I have found it to be quite accurate in the past.
Hope this helps! God Bless!