Courtesy Lamp: Description and Operation

Generic Electronic Module (GEM)
The Generic Electronic Module (GEM) receives inputs from the following:
^ ajar switch
^ headlamp switch
^ keyless entry keypad
^ Antilock Brake System (ABS) module wheel speed sensor signal
^ ignition switch
^ remote keyless entry transmitter

The GEM uses these inputs to control the output to the battery saver relay and interior lamp relay. Both relays are accessible from the Central Junction Box (CJB).

Interior Lighting Systems
The GEM grounds the battery saver relay and interior lamp relay coils when any ajar switch, or the interior lamp (headlamp) switch is closed. The interior lamp relay then supplies voltage to the interior lamp circuit. Vehicle speed must be less than 24 kph (15 mph) for the GEM to ground the interior lamp relay. The interior lamps will remain illuminated for up to 25 seconds after all doors are closed unless the GEM receives an input from any of the following:
^ voltage from the ignition switch
^ a vehicle speed signal
^ input from the keyless entry keypad
^ input from the remote keyless entry transmitter unlock or panic switch

Illuminated Entry
Illuminated entry is activated when a keyless entry keypad switch provides an input to the GEM or when the GEM receives an unlock signal from the remote keyless entry transmitter. The GEM then activates the battery saver and interior lamp relays by providing ground to the relay coils. Illuminated entry is deactivated when the GEM receives a lock signal from the remote keyless entry transmitter or if the GEM receives an input from the keyless entry keypad. Illuminated entry will also be deactivated when the GEM receives input voltage from the ignition switch.

Battery Saver
The battery saver is activated when the GEM is not receiving voltage input from the ignition switch (off position). The GEM will then provide ground to the battery saver relay coil, activating the relay, for a period of 10 minutes with the interior lamp (headlamp) switch in the off position, or a maximum period of 45 minutes with the interior lamp (headlamp) switch in the on position, provided that the GEM does not receive any other input signals within the time-out period. The activated battery saver relay switches voltage to the demand lamp circuit and the interior lamp relay coil. After time-out, the GEM disconnects ground from the battery saver relay coil disabling the demand lamp circuit.