power door locks

I was wondering if anyone out there new what could be the problem with my door locks and horn. I have power door locks on my 99 sport cherokee and here is the problem. When I go to lock the doors two of my doors make a buzzing sound and will not lock. I am guessing my door locks need to be replaced?? Some times they buzz but sometimes they will not and work. The only other problem I have is my horn went out. It still works from the steering wheel but not when I push the lock button on my remote. I don't get it...
If anyone has an idea or need more info please let me know. Thanks so much!

For the other problem:
Hold down the lock button on the remote for 5-10 seconds and press the unlock button while holding down the lock button. That should turn the chirp on or off

For the non-locking problem, you'll probably need some new parts inside the door. There are some plastic parts that go south eventually....I have the actuator for my 2000 GC, but haven't put it in yet. (Figuring that the doors can be locked manually)

Thanks for the help... my horn works again but need to get to work on the doors. Not to much of a priority because I can still lock and unlock manually. I have to work on the hub cap because it just broke off.
Thanks again

One of the "flipper"s is sticking or the lock it self.
This causes the switch to be out of sync. I use a workaround..unlock then lock, when this happens.

Glad I could help. My stealership buddy showed me how to do it. I was like WHAT?! I didn't know I could have a lock-beep! COOL!

Try taking the door panel off and lube the the sticking one. That is, the lock mechanism and linkage for the flipper.

Glad I could help. My stealership buddy showed me how to do it. I was like WHAT?! I didn't know I could have a lock-beep! COOL!

I turned mine off...annoying loud horn that does nothing to deter thieves...oh well Just MHO..

Thanks for the responses.. I did try to lube the locks and what not inside the door but I didn't notice a change. Does anyone know a website that I can order the parts for cheap and how about a website I can get a center cap from for my 99 cherokee? I am a teacher and need a cheap part website.
Thanks everyone!