I have a 2000 E-150 Econoline Conversion van with an interior light problem. The interior lights will not illuminate when a door is opened or the engine is running. They will illuminate when switched on individually, but do not respond to the master control (headlight switch). It seems as if the courtesy entry timing module has failed; previously when a door was opened the interior lights illuminated until a time delay lapsed, then the lights would shut off. Where is the module located that controls the entry lighting circuit, and how can I troubleshoot it?