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 is 10 minutes, as described by the Owner's Literature. For the accessory delay relay, refer to Windows.

The SJB communicates via the Medium Speed Controller Area Network (MS-CAN).

The SJB controls the power door lock system. The SJB monitors the door lock/unlock switch inputs from the interior door lock switches. When the SJB receives an unlock/lock command from any door lock control switch, the module activates the door lock actuators. Refer to Locks.

The SJB also controls the following remote lock/unlock features:

- Remote Keyless Entry (RKE) transmitter lock/unlock
- Panic alarm (button is part of the RKE transmitter)
- Keyless entry keypad

The SJB controls the autolamp subsystem. The autolamp subsystem provides light-sensitive automatic on/off control of the headlamps and parking lamps.

The SJB controls the battery saver, delayed accessory function, the horn, and exterior and interior lighting.

The SJB controls the Tire Pressure Monitoring System (TPMS).

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 that time of the fault event and a cumulative counter is started.

The module resets the FET protection and after a customer demand of the function (switching the component on, battery saver being energized), attempts to provide the requested output (voltage or ground). Each time the module detects an excessive load on the protected circuit, the counter advances.

When the excessive circuit load occurs 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 established in the module based on each circuits' total protective capability. For example, if the total predefined tolerance level is 600 fault events, the tolerance levels are reached at 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 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 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 headlamp system are for the LH low beam output and the RH low beam output circuits.