The 2 door switches input ground to the Central Locking Pump / Security System Module on pins 14 & 16.
This module then inputs to the Body Control Module on pins 52 & 78.
The BCM then decides whether or not to supply ground to the interior light switch on pin 3.

Piece of cake !!!

( there is a schematic and troubleshooting procedure in the service manual available under the link kindly provided by Mr. 180 in all his posts. )