Limited. What is causing battery drain?

To find out what is draining the battery do a parasitic draw test . How To Perform Parasitic Draw Test EricTheCarGuy Test to be sure , before replacing GEM module .I would also have the GEM checked for DTC'S - diagnostic trouble codes . I would also check the battery saver relay .
SECTION 417-02: Interior Lighting 2000 Explorer/Mountaineer Workshop Manual DESCRIPTION AND OPERATION Procedure revision date: 06/17/1999 Interior Lighting The interior lighting system consists of the following:

• dome/map lamp
• rear dome/cargo lamp
• overhead console/map lamp
• RH/LH vanity mirror
• ash receptacle lamp
• puddle lamps
• interior lamp switches
• interior lamp relay
• dimmer module
• battery saver relay
• generic electronic module (GEM)

Generic Electronic Module (GEM)/Central Timer Module (CTM) Controlled Functions
The generic electronic module (GEM) is equipped on four-wheel drive vehicles with power windows. The central timer module (CTM) is equipped only on two-wheel drive vehicles without power windows.
NOTE: GEM/CTM diagnostics are compatible with the scan tool.
The GEM/CTM incorporates the functions of several different modules into one, and offers diagnostics to easily locate and repair concerns affecting the subsystems that it controls.
The GEM/CTM constantly monitors the systems it controls and reports a concern in the form of a diagnostic trouble code (DTC). A DTC can be retrieved with the scan tool through the communication link.
The scan tool is a menu-driven tester that allows the user to run specific tests. The scan tool can isolate faults in the GEM/CTM subsystems through a symptom-driven diagnostic procedure. Connecting the scan tool to the GEM/CTM communication link will not alert the GEM/CTM. If the GEM/CTM is "asleep" when the diagnostic connector is plugged in, the GEM/CTM must be "awakened". If the communication link cannot be established, turn the ignition to RUN.
NOTE: The GEM/CTM has a sleep function to minimize battery consumption. During the sleep mode, the GEM/CTM turns off all outputs and monitors only the following:

• door ajar (driver door, passenger door, liftgate, LH rear and RH rear doors).
• key-in-ignition.
• key in RUN or ACC.
• two-step unlock switch (unarm switch).
• digital TR sensor.
• illuminated entry request (remote anti-theft personality [RAP] module).

If a change of status occurs at one of these inputs while the GEM/CTM is "asleep", the GEM/CTM will "wake up." When the GEM/CTM awakens, it carries out an internal self-test, and begins normal operation. At this point, the GEM/CTM will have all of its functions operational.
The GEM/CTM will go into the sleep mode immediately after both of the following conditions have been met:

• key in OFF or key not in ignition.
• after 45 minutes with no change in any wake-up input.

The GEM/CTM control system has two modes of operation; the normal operating mode and the tester-dependent diagnostics mode.
Normal operation of the GEM/CTM can detect errors. An integral part of normal GEM/CTM operation is continuous diagnostic capability. Continuous diagnostics detects errors and changes the GEM/CTM control strategy. There is no warning lamp for the GEM/CTM; therefore, a DTC concern will direct you to the GEM/CTM. Examples of faults that may be detected during normal operation include:
NOTE: The GEM/CTM can only detect open circuit/short to GRD faults when the GEM/CTM is not energizing a load, and short to battery faults when the GEM/CTM is attempting to energize a load.

• GEM/CTM continuous self-test (RAM, ROM, EEPROM, A/D checking).
• output driver monitoring (open circuit/short to ground [GRD], short to power).

• illogical combinations of input signals.