Honda Car Forum

This just worked for a 2000 Accord.

Storing transmitter codes:
The codes of up to three transmitters can be read into the keyless
receiver unit memory. (If a fourth code is stored, the code which was
input first will be erased.)

NOTE: It is important to maintain the time limits between the steps.
Make sure the doors and the hatch are closed.

1. Turn the ignition switch ON (II).

2. Within 1 to 4 sec., push the transmitter unlock button.

3. Within 1 to 4 sec., turn the ignition switch OFF.

4. Within 1 to 4 sec., turn the ignition switch ON (II).

5. Within 1 to 4 sec., push the transmitter unlock button.

6. Within 1 to 4 sec., turn the ignition switch OFF.

7. Within 1 to 4 sec., turn the ignition switch ON (II).

8. Within 1 to 4 sec., push the transmitter unlock button.

9. Within 1 to 4 sec., turn the ignition switch OFF.

10. Within 1 to 4 sec., turn the ignition switch ON (II).

11. Within 1 to 4 sec., push the transmitter unlock button.

12. YOU SHOULD NOW HAVE HEARD THE SOUND OF THE DOOR LOCK ACTUATORS!
On the same transmitter, push the unlock button AGAIN.

13. Within 10 sec., push the unlock button on up to two OTHER transmitters.

14. Turn the ignition switch OFF, and pull out the key.

15. Confirm proper operation of each transmitter.

The computer stores up to three transmitter identifier codes. By performing the above procedure, you empty the storage and refill it with up to three new codes. As such, if you have one working transmitter and one nonworking transmitter, and you only do this procedure with the nonworking transmitter, the working one will no longer work; you will have purged its code. You thus need to have ALL of your transmitters handy for Step 13.

Step 14 is key. It tells the car that the programming is over. Doing anything else resets the codes to their state before Step 1.

If you're explaining this to your mom over the phone, as I was, say
ON UNLOCK OFF, ON UNLOCK OFF, ON UNLOCK OFF, ON UNLOCK -- and then UNLOCK once on each keyfob -- OFF, remove key. It only took two tries, bless her heart.