1997 plymouth voyageur locks lock and unlock and interior lights flicker on and off while driving

The "BCM" module on your van has become unreliable.
The BCM is the "Body Control Module" that all these systems go through. The issue is that these are cold soldered and after a time the solder joints break on the computer connection. It is located behind the fusebox underneath the steering wheel.
If you know someone who can solder. You can use an 8mm and a 10mm socket to remove the BCM. Open it up and resolder the joints with a soldering iron. After that everything should be fine.
It is easier than it sounds.

BODY CONTROL MODULE
REMOVAL
Disconnect battery negative cable.
Remove lower steering column cover and knee blocker reinforcement.
Disconnect two wire connectors from bottom of Body Control Module (BCM) Body Control Module .
Remove bolts holding junction block (fuse Panel) to dash panel mounting bracket.
Remove junction block from mounting bracket.
Remove screws holding BCM to junction block.
Slide BCM downward to disengage guide studs on junction block from channels on BCM mounting bracket.
Remove BCM from junction block.
Re-solder Main connection points
INSTALLATION
Reverse the preceding operation.