Mazda 2003 MPV door locks

I just fixed this same problem. It happened to me 3 different times in a month so I got good at it. Before you dive into removing your door try this. Pull the door handle and release it letting it snap back several times. The problem is a half open door latch that won't let the door unlock. Do this as aggressively as you can to attempt to get the latch to return to its original position. Check the door lock between flicks.

Ok, if that didn't work, here is how to remove the door.
1. Remove the screw behind the door latch, you will have to pop the plastic cover off first.
2. Remove the rubber insert in the door handle
3. Remove the screw that is now visible
4. Now remove the window/lock control module, the back is free but the front has a plastic lip so lift the back up and pull towards the back of the van.
5. Remove the clips that attach to the lock and to the window controls (these can be a pain)
5. (Optional) Remove the bracket that held the window/lock control module

At this point your door is basically free, it is only held in place with plastic clips that can be easily forced off. If your door were open you would simple pull the bottom of the door out (hinged at the window) and lift it off. But since we can't pull because the door is closed we have to force it out.

From here it is pretty simple. Move the seat all the way back and tip the seat way back. Lift the door panel straight up. You will be breaking 2 plastic clips from the rear part but once you do it just pulls out. This is not that easy because the space is limited but just keep pulling and force the rear end of the door panel past the b-pillar. Once you do this it is free.

Have fun and try to keep the black gook from getting everywhere.

Oh, to fix the door lock just oil/grease it and manually move the mechanism several times.

I also had this problem but on the driver side and the aggressive handling of door handle in and outside didn't do anything. I opened up door panel of the opposite 'good' door to practice, which later proved to be the key. After playing with the good door I followed the instruction of Davissc up to #5. But before continuing to break the two plastic white clips. Because removing the door panel is hard as the moving space is small. Try the following before breaking things.
-Investigate the lock mechanism closely on the good door. The lock indicator and door lever (inside the car) mechanism work with two cables like bicycle brakes cables. The top one pushes and pulls the lock indicator, the bottom release the door latch. The lock indicator can not be switched when the lever cable is pulled at. Now you should be ready to use this on the stubborn door/lock.
- Try to push cable (bottom cable) back with small pliers or better small vise grip. It was possible to push back the cable into the cable guide when holding it very close to the entry of the cable guide. (Sounds easier then in real life, took me 45 mins) After which I tested the lever and was luck the door opened!!
Now the removing the door panel was a breeze. Followed by gently removing the rods from the outside door lever and key. After removing the 3 bolts from the lock and the plastic protection cover (one small screw) the cause the the lock jam was very clear. Some metals parts were oxidised cause friction on the levers and springs. After brushing, WD40 and some grease the lock worked fine again.
Yes, it works again!!, Thanks Davissc, hope others will also have fun with the black goo, it was even in my hair after a one of the many close inspections of the look.

For the door lock jamming, the handle snapping trick worked for me but it kept reoccuring. The solution that worked for me was to spray WD-40 on the door handle as advised by an Autozone agent.