Principles of Operation
Locks, Latches and Entry Systems
Principles of Operation
NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).
The SJB receives inputs and delivers outputs to many of the electronically controlled features of the vehicle. The SJB constantly monitors the system under its control and reports a concern in the form of a DTC.
Power Locks
The SJB monitors the door lock control switches and Integrated Keyhead Transmitters (IKTs) . When the SJB receives a lock/unlock command from a door lock control switch or an IKT, the SJB energizes the appropriate lock or unlock relay to supply voltage to the door lock actuator circuit(s). The door lock actuator circuits are at ground through the SJB when the lock and unlock relays are not energized.
Keyless Entry Keypad
The SJB monitors the keyless entry keypad input. When the correct codes are entered into the keypad, the SJB carries out functions associated with the code entered. Based on input from the keypad, the SJB:
- locks all doors.
- unlocks the driver door.
- unlocks all doors.
- opens the luggage compartment lid (Taurus, Sable).
- recalls memory seat/power mirror positions (if equipped).
- enters programming mode.
- enables/disables the autolock feature.
- enables/disables the auto-unlock feature.
Remote Keyless Entry (RKE)
The SJB receives input from programmed Integrated Keyhead Transmitters (IKTs) . Based on input from the IKT, the SJB:
- Locks all doors
- Unlocks the driver door (with stepped unlock enabled)
- Unlocks all doors
- Activates/deactivates the panic alarm
- Arms/disarms the perimeter alarm (if equipped)
- Releases the luggage compartment lid latch (Taurus, Sable)
- Releases the liftgate latch (Taurus X with power liftgate)
- Activates the memory positions (if equipped).
- Turns the interior lamps on (when unlocking) and off (when locking), provided the defeat switch on the dimmer switch is not active
- Sounds the horn once when LOCK is pressed twice within 3 seconds, and the doors and luggage compartment lid or liftgate are closed
- Sounds the horn twice when LOCK is pressed twice within 3 seconds, and any door, luggage compartment lid or liftgate is open
- Flashes the turn signals once each time LOCK is pressed, and the doors and luggage compartment lid or liftgate are closed.
- If any door is ajar, the turn signals will not flash when LOCK is pressed, until all doors and luggage compartment lid or liftgate are closed.
Luggage Compartment Lid Release
The luggage compartment lid release switch operates the luggage compartment lid latch electronically. When the switch is pressed, the SJB processes the input and releases the luggage compartment lid latch.
Liftgate Release
The liftgate release switch operates the liftgate latch electronically. When the switch is pressed, the SJB processes the input and releases the liftgate latch.
The doors must be unlocked electronically in order for the SJB to release the liftgate latch. When this condition is met and the SJB receives the input from the liftgate release switch, the SJB provides power to the latch.
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 for 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 does not clear by a command to clear the continuous DTCs. The module does 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 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. These DTCs cannot be cleared and the module must be replaced.
The SJB FET protected output circuits for the handles, locks, latches and entry systems are the liftgate lock actuator circuit CPL10 (GN/WH) and the keypad illumination circuit CPK28 (WH/GN).