push the door switches in by hand and see if the lights go out. Here's some diagnostic info:
Vehicles may be equipped with either a generic electronic module (GEM) or a central timer module (CTM) depending on vehicle options.
- Vehicles with 4-wheel drive or the power group option will be equipped with a GEM.
- Vehicles with 2-wheel drive and no power group option will be equipped with a CTM.
The GEM and the CTM illuminate the interior lamps when any door is open or ajar. The interior lamps are: the interior lamp, the cargo lamp and the door courtesy lamp. The courtesy lamps will shut off when:
- The doors are closed and the illuminated entry (GEM only) feature is not active.
- The vehicle speed is greater than 15 mph (24 km/h). The interior lamps will not be reactivated until the vehicle speed is less than 10 mph (16 km/h) and a new door open warning lamp switch signal is received (GEM only).
The system inputs to the GEM/CTM are as follows:
- The door open warning lamp switches. (Grounded when door is ajar; an open circuit when the door is closed.)
- The vehicle speed sensor (VSS) input. (Sinusoid Wave: 0.7V-20V, 2.2 Hz/MPH [1.37 Hz/km/h] [GEM only].)
The system output to the GEM/CTM is as follows:
- The interior lamp relay coil output. (Grounded when activated; open circuit when deactivated.)
Interior Lamp Relay
The GEM and the CTM control the interior lamps and illuminated entry function with the interior lamp relay.
The relay is activated by applying ground to the relay coil through GEM C267-15, and is deactivated by removing the ground signal.
Panel Dimmer Switch
The panel dimmer switch is integrated into the headlamp switch and controls the interior lamps by activating the interior lamp relay.
Illuminated Entry (GEM Only)
The GEM illuminates the interior lamps when an unlock signal is received from the remote anti-theft personality (RAP) module. The illuminated entry feature will be canceled when any of the following conditions are met:
- 25 seconds have elapsed since the illuminated entry feature was activated and the courtesy lamp feature is not activated.
- The GEM receives a request from the RAP module (remote transmitter lock button pressed) and the courtesy lamp feature is not activated.
- The ignition is in the RUN or START position and the courtesy lamp feature is not activated.
The illuminated entry inputs are:
- RAP illuminated entry request. (Grounded pulse of varying length.)
- Ignition switch in the RUN position. (Battery voltage on both the RUN and RUN/ACC inputs.)
The illuminated entry outputs are:
- Interior lamp relay coil output. (Grounded when activated; an open circuit when deactivated.)
The RAP module sends a signal to the GEM on the illuminated entry request circuit to indicate a request to turn the illuminated entry feature on or off. Circuit 1013 (BR/LG) is normally sent 12 volts by the GEM. The RAP module shorts this circuit to ground with a pulse of either of the following lengths:
- 200 ms pulse from RAP receiver assembly requests illuminated entry ON (unlock button pressed).
- 300 ms pulse from RAP receiver assembly requests illuminated entry OFF (lock button pressed).
GEM Sleep Mode
The GEM and the CTM sleep mode deactivate all outputs to conserve battery power. Sleep mode is entered when the ignition has not entered the RUN or ACC position and 45 minutes has elapsed since the last wake-up input was received. In this mode, GEM current consumption is reduced to 5.0 mA or less. During sleep mode the GEM monitors the following wake-up inputs:
- Both front door open warning lamp switches.
- Ignition switch in the key-in, ACC and RUN position.
- RAP illuminated entry request.
The GEM sleep mode outputs are:
- None. (All circuits are deactivated during sleep mode.)
If a change in any of the above inputs occur while the GEM is asleep, the GEM will wake up and monitor all of its inputs and have the ability to activate any of its outputs.
The following components are under the control of the battery saver relay:
- Interior lamp.
- Engine compartment lamp.
- Glove compartment lamp.
- Panel dimmer switch.
- Interior lamp relay.
The battery saver relay becomes active (relay coil is energized) when the GEM is in the awake mode, and is deactivated (relay coil is de-energized) in the sleep mode. The battery saver will remain active until the ignition switch is removed from the ACC or RUN position and 45 minutes have passed since the last active input was received (see sleep mode inputs). At that time, the relay will be deactivated and power to the above circuits will terminate.
The battery saver inputs are the GEM sleep mode inputs.
The battery saver output is the battery saver relay.
Inspection and Verification — GEM/CTM
- The interior lighting system is a generic electronic module (GEM)/central timer module (CTM) controlled system. Refer to Section 419-10 for additional information regarding GEM/CTM diagnostic strategies.
- Verify the customer concern by operating the interior lamps.
- Visually inspect for obvious signs of mechanical and electrical damage.
Visual Inspection Chart
- Fuse(s) 14 (15A), 15 (5A), 4 (5A), 8(5A), and 103 (50A).
- Wiring harness
- Loose or corroded connector(s)
- Circuitry open/shorted
- If the concern remains after the inspection, connect the New Generation STAR (NGS) Tester to the data link connector (DLC) located beneath the instrument panel, and select the vehicle to be tested from the NGS menu. If the NGS does not communicate with the vehicle:
- check that the program card is correctly installed.
- check the connections to the vehicle.
- check the ignition switch position.