Principles of Operation

Interior Lighting

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 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 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 request is detected from the instrument panel dimmer switch, 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 Field-Effect Transistor (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 of the fault. The circuit then resets 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 can not be cleared by a command to clear the continuous DTCs. The module does 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 clears and the circuit function returns.

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.