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 one 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 battery saver relay, refer to Courtesy Lamp. For the accessory delay relay, refer to Windows. Courtesy Lamp

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, exterior and interior lighting and the horn.

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 shorted circuits) and are shut down (turn 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 reset after a customer demand (ignition cycle) of the function (which will switch the component on, causing the 30-minute battery saver timer to be energized). When an excessive circuit load (from a shorted circuit) 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 by the first failure will not clear by a command to clear the continuous DTCs.

The SJB will not allow the DTC to be cleared or the normal circuit function restored until a successful self-test (retrieving on-demand DTCs) proves that the fault has been repaired. After the self-test has successfully completed (no on-demand DTCs present), the continuous DTC will have been cleared and the normal circuit function will be restored.

The SJB has three predefined levels of short circuit tolerance established. When the first or second level is reached, the continuous DTC associated with the short circuit sets along with DTC B106E. These DTCs (B106E and the DTC associated with the shorted circuit) may be cleared using the Clear DTC operation on the scan tool as long as the fault itself has been corrected. Each and every time the scan tool retrieves DTCs from the module and a circuit is shorted, a level of short circuit tolerance is used up.

If any of the circuits are shorted past the third level (if DTCs have been retrieved 3 successive times with the short circuit not having been repaired), then DTCs B106F and B1342 are set along with the associated continuous DTC. These DTCs (B106F and B1342) cannot be cleared and the module must be replaced.

The initial short circuit must be successfully repaired and its associated DTC is cleared before the SJB is replaced or the new SJB may experience one or more of the short circuit tolerance levels being used unnecessarily, causing a repeat replacement of the module.

DTC B106E sets when the SJB has disabled a circuit due to a repetitive fault causing a circuit overload. A corresponding DTC for the circuit in question will also be set.