Principles of Operation

PRINCIPLES OF OPERATION

NOTE: The smart junction box (SJB) is also known as the generic electronic module (GEM).

The SJB supplies voltage to the interior lighting system. The interior lighting system illuminates the courtesy lamps to enhance visibility of the interior while a vehicle door is open or ajar, and the vehicle speed is less than 15 km/h (9 mph). The SJB controls all interior lighting functions and timing by monitoring inputs from the door ajar switches, liftgate ajar switch, liftgate glass ajar switch, instrument panel dimmer switch, and vehicle speed.

Interior Lighting Delay
The interior lighting delay feature provides temporary illumination of the courtesy lamps after the doors are opened and then closed. The interior lighting delay feature will keep the courtesy lamps on for a period of 25 seconds. If during the 25 second delay time the SJB detects that the ignition has been turned to RUN, ACC, START, or if the vehicle is locked using the remote keyless entry (RKE) transmitter, the courtesy lamp illumination will be discontinued.

Illuminated Entry
The illuminated entry requests the courtesy lamps to be illuminated when the ignition is OFF and the RKE transmitter UNLOCK button is pressed. The illuminated entry requests the courtesy lamps off after 25 seconds have elapsed, the ignition is switched to ON, or when the RKE transmitter LOCK button is pressed.

Illuminated Exit
The illuminated exit requests the courtesy lamps be illuminated for 25 seconds when all doors are closed and the ignition key is removed from the ignition lock cylinder. The illuminated exit will request the courtesy lamps be deactivated when any door becomes ajar, the ignition key is inserted into the ignition lock cylinder, or 25 seconds have elapsed.

Theater Lighting
The theater lighting option ramps-up the courtesy lamps over 0.7 seconds when courtesy lamp activation is requested. The theater lighting feature ramps-down the courtesy lamps over 1.7 seconds when interior lighting deactivation is requested by any feature other than the panic alarm or battery saver.

Interior Lamp Arbitrator
The interior lamp arbitrator (located in the SJB) chooses between the interior lighting, interior mode, interior lighting delay, illuminated entry, illuminated exit, battery saver, and alarm flash processing to determine which feature has precedence of activating and deactivating the interior lamps. The features are prioritized as follows: alarm flash processing, battery saver, interior mode, interior lighting, interior light delay, illuminated entry, and illuminated exit.

Battery Saver
The battery saver is internal to the SJB and provides automatic shutoff of the demand lamps (vanity lamps, map lamps and glove compartment lamp) and courtesy lamps after a time-out period in order to save battery voltage. A timer in the SJB is started when the ignition is turned to the OFF position. When the time-out period for the lamps has elapsed, the voltage is automatically shutoff to the lamps by the battery saver. While the battery saver has voltage disabled, if the ignition is turned to any position other than OFF, any door or liftgate/glass becomes ajar or the UNLOCK button of the RKE transmitter is pressed, the battery saver will restore voltage and start the timer again.

NOTE: Time out is 1 minute if the vehicle has less than 80 km (50 miles).

The battery saver time-outs are as follows:
- Courtesy lamps if the dome lamp is off and the liftgate/liftgate glass is closed = 10 minutes
- Courtesy lamps if the dome lamp is on or the liftgate/liftgate glass is open = 30 minutes
- Demand lamps = 30 minutes

Field-Effect Transistor (FET) Protection
The SJB utilizes a FET protective circuit strategy for many of its outputs (for example, the headlamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down (turns off the voltage or ground provided by the module) when a fault is detected. A continuous DTC is stored at that time for the fault. The circuit will then reset after a customer demand of the function (switching the component on, battery saver being energized). When an excessive circuit load occurs several times, the module shuts down the output until a repair procedure is carried out. At the same time, the continuous DTC that was stored on the first failure will not clear by a command to clear the continuous DTCs. The module will not allow this code to be cleared or the circuit restored to normal until a successful on-demand self-test proves that the fault has been repaired. After the on-demand self-test has successfully completed (no on-demand DTCs present), the continuous DTC will have been cleared and the circuit function will return.

Each circuit has 3 predefined levels of short circuit tolerance established in the module based on each circuits' capability. When the first or second level is reached, the continuous DTC associated with the circuit sets along with DTC B106E. These DTCs may be cleared using the Clear DTC operation on the scan tool as long as the fault itself has been corrected. If any of the circuits are shorted past the third level, then DTCs B106F and B1342 set along with the associated continuous DTC. These DTCs cannot be cleared and the module must be replaced.

The SJB FET protected output circuits for the instrument panel illumination system are for the LED backlighting output circuits.