How do you Program a Honda Odyssey remote keyless fob?

I found this for the 2007 and it works for the 2008, too.

Important tip: It seems that the Odyssey can only have two remote keyless fobs programmed at once. Adding more removes the original ones.

If you are adding a new key then the key has to be reprogrammed by a Honda dealer as that vehicle has immobilizer on it and the key has a chip in it. you will need to have all keys available to reprogram at the same time. reprogramming changes the codes in the immobilizer unit so that only those keys will start the car. Honda dealers will charge you to reprogram the keys for the immobilizer.

if it is the remote keyless entry on the key fob that you want to reprogram you can do that yourself. Most Honda dealers will program the keyless remote for free. you can do it yourself if necessary. to program the remote you follow this procedure

you need to sit in the drivers seat with all of the doors closed for this programming procedure to work. leave the doors unlocked when you start the procedure. It is very helpful to detach the remote from the key so you have the key in one hand, and the remote in the other.

1. put the ignition key in the ignition but do not turn it on. hold the remote to be programmed in your left hand.

2) with your right hand, turn the ignition key to the ON position so that the lights on the dash come on. you do not need to start the car. within 3 seconds, push the LOCK button on the remote in your left hand.

3) turn the ignition key to the off position. then turn the ignition key to the ON position again. within 3 seconds press the LOCK button on the remote. then turn the ignition key OFF.

4) repeat that procedure 2 more times. on the 4th cycle you should hear the transmitter operate the door locks. and the doors should lock.

Programming transmitters for 2002, 2003 & 2004 Honda Odyssey Models, also follow these additional steps (may apply to other model years, but I haven't tested them)

5) Within 10 seconds of completing step 4, use the remote to LOCK or UNLOCK the doors. Then press the LOCK or UNLOCK button on each additional remote used for the vehicle.

6) Turn the ignition key to the OFF position, remove the key & verify all transitters are programmed to the vehicle.

Note: Step 5 actually registers each transmitter to the vehicle and also RE-registers a previously used tansmitter; if you do not follow this step for each and every remote used on the vehicle, the remote(s) will NOT work on the vehicle. (this is a commonly overlooked step for programming transmitters across many types of vehicles.)