Principles of Operation
The SJB is a multifunction module that controls many of the vehicle systems. Several SJB functions utilize hardwired inputs and/or outputs. The SJB controls the following hardwired functions, using the corresponding inputs and outputs
| Function | Input(s) | Output(s) |
|---|---|---|
| Daytime running lamps (DRL) (if equipped) | Headlamp switch Controller area network (CAN) messaging from instrument cluster | Low beam headlamps |
| Fog lamps (if equipped) | Headlamp switch | Fog lamp relay |
| Horn | Horn switch | Horn relay |
| Interior lighting | Door ajar switches Remote keyless entry (RKE) transmitter | Interior lamps relay |
| One-touch down driver window | Master power window switch | One-touch down relay |
| Parking lamps | Headlamp switch | Parking lamps relay |
| Power locks (if equipped) | Driver door lock control switch Passenger door lock control switch | Door lock/unlock relays |
| RKE system (if equipped) | RKE transmitter | Door lock/unlock relays Interior lamps relay |
| Tire pressure monitoring system (TPMS) | TPMS sensors | CAN message to instrument cluster |
| Windshield wipers/washers | Multifunction switch | Wiper run/park relay Wiper speed relay Washer pump relay |
In addition, the SJB is involved in other vehicle systems through communication over the CAN. For a detailed list of SJB network inputs and outputs, refer to MODULE COMMUNICATIONS NETWORK article, Principles of Operation.
Some SJB parameters are programmable. Two types of programmable parameters are available: vehicle configuration and customer preference. For additional information on programmable parameters, refer to MODULE CONFIGURATION article.
The SJB utilizes a 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 diagnostic trouble code (DTC) is stored at that time for the fault. The circuit will then reset 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 service procedure is performed. At the same time, the continuous DTC that was stored on the first failure will not clear by a command to clear the continuous DTCs. The module will 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 will have been cleared and the circuit function will return.
Normal Operation
The smart junction box (SJB) controls the output of the daytime running lamps (DRL), fog lamps, one-touch down driver power window, accessory delay, windshield wiper park/run, windshield wiper speed, and windshield washer. When a repetitive fault causing a circuit overload is detected on any of the output circuits, the SJB disables the circuit by removing voltage, or ground, to the affected circuit. The circuit remains disabled until the fault is corrected and an on-demand self-test is run. After the on-demand self-test has been run, any diagnostic trouble codes (DTCs) related to the fault will be cleared.
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 set as follows
- DTC B1304 - Accessory delay relay circuit short to B+
- DTC B1400 - One-touch down window relay circuit short to B+
- DTC B1432 - Windshield wiper park/run relay circuit short to B+
- DTC B1436 - Windshield wiper hi/low speed relay circuit short to B+
- DTC B1460 - Washer pump motor relay circuit short to B+
- DTC B2512 - Fog lamp relay circuit short to B+
- DTC B2973 - DRL output short to ground
DTC B106F - sets when one or more output functions are permanently disabled due to a repetitive circuit overload fault. DTC B106F will be set with DTC B106E. When DTC B106F is present, the SJB must be replaced after the fault condition has been corrected.
Possible Causes
- Output circuit short to ground or voltage
- SJB