I have just aquired a Doblo van 2004, I have a problem with locking the van, when I lock with the key it unlocks straight away, I can see that the dash is telling me that one door/s is open, any ideas how I can eliminate the doors to trace the problem ?, also out of interest, this van has covered 167k, whats the lifespan of these engines ?

I've the same problem as you, buyed used with 40000 km.
Seems that the contacts of the doors (expecially slide port) needs to be changed or cleaned, as it doesn't get contact immediately...

fixed temporarely with cleaning contacts with the antioxidant, but now it's the same.

Another home-made fix is to keep the key on lock position for a while, then to be sure: unlock the car, open and close a random door and close again the car.
This can work also if you are driving, by keeping the door's lock for a while... but don't open the door then the display will show you that the car is closed, so it's a good method.

I am especially careful when closing the tailgate as it seems to never shut quite properly at first (I notice the boot light stays on) due, I believe, to the pressure build up inside the car when closing - it's fine if windows are open or I release it slightly then close it.
The side doors also need a little extra 'oomph' at the last second as they also seem affected by internal pressure.
Might sound daft but it works for me

thanks for the replys, its the locking of the vehicle that concerns me rather than the dash warning, I want to try to trace which door is the problem but cannot see a process of elimination