I have a 2008 Toyota Highlander. If I lock the doors remotely and then go around to the trunk and pull the handle twice, all the doors (including the trunk) unlock and the interior lights illuminate. So basically, anyone can get into my locked car as long as they try the trunk twice.

SOURCE: 1998 Jetta Passenger Door Won't Unlock

I had a similar problem with my son's 1998 Jetta K2 4 door. I sprayed loads of WD40 into the locking area from the end of the door through the clip slot, worked the mechanism sprayed some more and finally it start working. My mechanic said these are very prone to moisture causing rusting on the moving parts.

SOURCE: remote starter does not work but will unlock and lock doors.

You need to first press the LOCK button and then immediately hold down the START button for 2 seconds - voila!

SOURCE: My key fob remote will not unlock car doors but will start car

Here you go.If you can't read it I can email it to you.

SOURCE: Mk4 Golf. Remote locking, windows and interior lights not working

Maybe fuse number 6 is blown (check lefthand side of steerning wheel where all teh fuses are located - you must open the door)

SOURCE: 2008 chevy malibu. cannot unlock doors from dirver

Intermittent door ajar switch contacts.