Do a search and find how to pull the doors interior off. This will allow you access to the doors locking mechanisms. Just look around and have a feel of everything that makes up the lock system. If you can find something obvious, thats great. Otherwise you may need a bit of electrical experience to find the problem (could be a failed solenoid). But do a search, there have been tips on problems. Couple of things that can go wrong, but no point me explaing them to you unless you know what your looking for. May just need the wd-40, or may be more than that, but best way is to have a look.