Principles of Operation
Interior Lighting
Principles of Operation
NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).
When a vehicle door or liftgate is ajar with the vehicle speed less than 15 km/h (9 mph) or 5 km/h (3 mph) for puddle lamps, or the instrument panel dimmer switch is in the DOME LAMP position, the SJB provides voltage to the interior courtesy and puddle lamp circuits. The SJB controls all interior lighting functions and timing by monitoring inputs from the door ajar switches, the liftgate ajar switch, the Liftgate/Trunk Module (LTM) (if equipped with a power liftgate), the instrument panel dimmer switch, the Remote Keyless Entry (RKE) transmitter and vehicle speed.
Interior Lamp Arbitrator
The SJB chooses between the interior lighting, interior lighting delay, illuminated entry, illuminated exit and battery saver to determine which feature has precedence of activating and deactivating the interior lamps.
Battery Saver
NOTE: Time-out is 1 minute if the vehicle has less than 80 km (50 miles).
The SJB provides automatic shut-off of the demand lamps and courtesy lamps after a 10-minute 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 are closed. When the 10-minute time-out period has elapsed, the voltage is automatically shut off to the lamps by the SJB. While the SJB has voltage disabled, the timer resets if any of the following occur:
- The ignition is turned to any position other than OFF.
- Any door becomes ajar.
- The UNLOCK button of the RKE transmitter is pressed.
- An unlock request from the door lock cylinder is received.
- A key is inserted into the ignition lock cylinder.
- A valid keypad code is entered.
- The instrument panel dimmer switch is placed in the DOME LAMP position.
- The headlamp switch is placed to the PARKING LAMPS or HEADLAMPS ON position.
- The multifunction switch is placed in the FLASH-TO-PASS position.
- The key is inserted into the ignition lock cylinder.
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 event is detected. A continuous DTC is stored at the fault event and a cumulative counter is started.
When the demand for the output is no longer present, the module resets the FET circuit protection. The next time a request activates a circuit that has been shut down by a previous short (FET protection) and the circuit remains shorted, the FET protection shuts off the circuit again and the cumulative counter advances.
When the excessive circuit load occurs often enough, the module shuts down the output until a repair procedure is carried out. Each FET protected circuit has 3 predefined levels of short circuit tolerance based on the harmful effect of each circuit fault on the FET and the ability of the FET to withstand it. A total level of fault events is established based upon the durability of the FET. If the total tolerance level is determined to be 600 fault events, the 3 predefined levels would be 200, 400 and 600 fault events.
When each tolerance level is reached, the continuous DTC that was stored on the first failure cannot 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 operation until a successful self-test proves that the fault has been repaired. After the self-test has successfully completed (no on-demand DTCs present), the continuous DTC automatically clears and the circuit function returns.
When the first or second level is reached, the continuous DTC (associated with the short circuit) sets along with DTC B106E. These DTCs can be cleared using the module self-test, then the Clear DTC operation on the scan tool as long as the fault itself has been corrected.
If the number of short circuit fault events reach the third level, then DTCs B106F and B1342 set along with the associated continuous DTC. This DTC cannot be cleared and the module must be replaced.
The SJB FET protected output circuits for the interior lighting system are the puddle lamp and courtesy lamp output circuits.