My 2005 CCSB has decided not to lock the rear door power locks. Doesn't matter whether I use the door switch or key fob. The locks refuse to lock, but will unlock with the other doors.

Any ideas?

did you check the child safety lock on the door itself? it might be partway on.

Mine has done this more than a few times too. I usually just, using the remote, keep locking and unlocking till it works. Have had to do it sometimes 6-8 times. I also have some 'magical' words that help.

you need new relays thats what fixed mine