Principles of Operation

PRINCIPLES OF OPERATION

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

The smart junction box (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 ajar, and the vehicle speed is less than 15 km/h (9 mph) or 5 km/h (3 mph) for puddle lamps. The SJB controls all interior lighting functions and timing by monitoring inputs from the door ajar switches, the 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 keeps the courtesy lamps on for a period of 25 seconds after all the doors, decklid or luggage compartment are closed. If during the 25 second delay time the SJB detects that the ignition has been turned out of OFF, or if the vehicle is locked using the integrated keyhead transmitter (IKT) or the keypad, the courtesy lamp illumination is discontinued.

Illuminated Entry
The illuminated entry requests the courtesy lamps to be illuminated when the ignition is OFF and either the IKT transmitter UNLOCK button is pressed, or the vehicle is unlocked using the keypad or driver door lock cylinder. The illuminated entry requests the courtesy lamps off after 25 seconds have elapsed, the ignition is switched out of OFF, the IKT transmitter LOCK button is pressed, or the vehicle is locked using the keypad.

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

Theater Lighting
The theater lighting option ramps-up the courtesy lamps over 0.7 second 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 SJB chooses between the interior lighting, interior mode, interior lighting delay, illuminated entry, illuminated exit and battery saver to determine which feature has precedence of activating and deactivating the interior lamps.

The features are prioritized as follows:
- Perimeter alarm/panic alarm
- Battery saver
- Interior lighting
- Interior light delay
- Illuminated entry
- Illuminated exit

Battery Saver
The SJB provides automatic shut-off of the demand lamps 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, and all the doors, and the liftgate or the luggage compartment are closed. When the time-out period for the lamps has elapsed, the voltage is automatically shut off to the lamps by the SJB. While the SJB has voltage disabled, if the ignition is turned to any position other than OFF, any door, liftgate or luggage compartment becomes ajar, or the UNLOCK button of the IKT transmitter is pressed, a valid keypad code is entered, an unlock request from the cylinder is received, or the dome lamp switch is turned on, the SJB restores voltage and starts 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 = 10 minutes
- Demand lamps = 10 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 an ignition cycle or customer demand of the function (switching the component on, 30-minute 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. This DTC cannot be cleared and a new module must be installed.

The SJB FET protected output circuits for the interior lighting system are for the puddle lamps and courtesy lamp output circuits.