If you mean while driving, it's a normal safety feature that the power door locks engage when the vehicle exceeds 30 Km/h or 20 Mi/h.
If you mean that there seems to be a malfunction causing the door locks to constantly engage when they aren't supposed to, then the likeliest culprit is a faulty switch in one of the doors, or possibly a short in the wiring to the switch. The common places to find wiring problems would be either at the door jamb where the wires get flexed repeatedly, or near the switch.
It is on the driver's door.
most likely the lock actuator plastic gears a stripped and slipping go get a new lock actuator
If the Montero's horn sounds continuously when doors are locked with the remote, this is due a horn pad failure. To repair, replace the horn pad assembly.
Lock doors with electric.
Press lock tab in and then pull.
The door lock actuator is going bad.
take the van to the dealer and have the body computer up dated the easiest way to see if this will work is to unhook the battery and if the locks go back to working it will fix it
Use the remote door lock to lock the doors, then unlock, then lock. The alarm should be reset. If not get in the vehicle, lock all the doors with them closed, unlock them, relock them walla alarm reset!
Many of the newer vehicles automatically lock the doors when the vehicle starts to move. Some have provision to disable that feature, but most do not.
bad ground on chassis. do the lights seem dim when you apply the brakes?
To increase caravan security, you can attach wheel lock clamps. You can also have security lighting and make sure all the windows, doors and entrances are locked securely.
check the door lock master switch usually that is the problem