Today I found out that I've been leaving my car unlocked for who knows how long because the doors haven't been locking. When I use the remote as I walk away the lights flash and the horn chirps, but it's all been a lie...

The doors unlock fine, but will not lock regardless of what switch I use. What would cause this? I hear a relay clicking from behind the cluster when I press the lock button, could a faulty relay cause such a thing?

I changed my passenger power DL switch because it only unlocked and didn't lock, so I went to the JY got a replacement changed it and its workin good as new. You can also program the keyless entry, mine just blinks 2 twice and before I walk out the car I push the DL down and it does lock all doors in a few seconds. Relays im not familiar with all I now is the fuse panel by interior trim panel next to the passenger door and the relays under the fuse panel under the hood.

Sounds like it could be a relay. I'd check that first.