Principles of Operation

Smart Junction Box (SJB)

Principles of Operation

NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

NOTE: The time out for the battery saver relay and the accessory delay relay (both are controlled by the SJB) is 1 minute if the vehicle has less than 80 km (50 miles). Once the vehicle passes the approximate mileage threshold of 80 km (50 miles), the time out for both relays will be the normal 10 minute time out, as described in the Owner's Literature. For the battery saver relay, refer to Courtesy Lamp. For the accessory delay relay, refer to Windows. Testing and Inspection

The SJB is a multifunction electronic module that controls many of the vehicle systems. Most of the SJB functions utilize hardwired inputs and/or outputs. The SJB controls the following hardwired functions, using the corresponding inputs and outputs:





In addition, the SJB is involved in other vehicle systems through communication over the Medium Speed Controller Area Network (MS-CAN). For a detailed list of SJB network inputs and outputs, refer to the Principles of Operation in Information Bus. Principles of Operation

Some SJB parameters are programmable. Two types of programmable parameters are available: vehicle configuration and customer preference. Refer to Information Bus.

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 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 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 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 the module must be replaced.

The SJB FET protected output circuits for the headlamp system are for the LH low beam output and the RH low beam output circuits.