Principles Of Operation

Locks, Latches and Entry Systems - Integrated Keyhead Transmitter (IKT)







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 an issue in the form of a DTC.





Power Door Locks

The SJB controls all of the passenger door lock actuators and receives input from the passenger door lock control switch. The Driver Door Module (DDM) controls only the driver door lock actuator and receives input from the driver door lock control switch. The two modules communicate the lock or unlock commands through the Medium Speed Controller Area Network (MS-CAN).

The SJB and the DDM are supplied voltage at all times. When the SJB receives a signal from the Remote Keyless Entry (RKE) transmitter, the keyless entry keypad, or the RH door lock control switch, the SJB sends a command to the DDM through the MS-CAN, and a ground signal to the lock and unlock relays. When the LH door lock control switch is pressed, the DDM receives the lock or unlock signal. The DDM sends a request through the MS-CAN to the SJB to lock or unlock the passenger doors. The SJB then responds to the DDM request, authorizing a lock or unlock of the driver door by the DDM. The DDM then supplies voltage and ground to the driver door lock actuator based on the lock or unlock request. The ground signal in the SJB closes the relay which supplies voltage to the remaining door lock actuators. The remaining door lock actuators then actuate to a lock or unlock position determined by the relay.

Luggage Compartment Lid Release

NOTE: When using the Integrated Keyhead Transmitter (IKT), 2 presses of the luggage compartment lid release button (within 3 seconds) are required to release the luggage compartment lid.

The luggage compartment lid release system is inhibited when the vehicle speed exceeds 8 km/h (5 mph). The luggage compartment lid latch releases the luggage compartment lid when the customer requests it opened using either the IKT, the keyless entry keypad, or the luggage compartment lid release switch. When the SJB receives a signal to release the luggage compartment lid, the SJB supplies voltage to the luggage compartment lid latch. The luggage compartment lid latch then actuates to release the luggage compartment lid.

Remote Keyless Entry (RKE)

The SJB receives input from the programmed IKT. 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
- Releases the luggage compartment lid latch
- Activates the memory positions
- Turns the interior lamps on (when unlocking) and off (when locking)
- Sounds the horn once when LOCK is pressed twice within 3 seconds, and the doors and luggage compartment lid are closed
- Sounds the horn twice when LOCK is pressed twice within 3 seconds, and any door, or the luggage compartment lid is open
- Flashes the turn signals once each time LOCK is pressed, and the doors and luggage compartment lid are closed
- If any door is ajar, the turn signals will not flash when LOCK is pressed, until all doors and luggage compartment lid are closed

Keyless Entry Keypad

NOTE: The keyless entry keypad does not lock the doors if the driver door is ajar.

The keyless entry keypad is hardwired to the SJB. The SJB interprets the inputs from the keyless entry keypad and then controls the associated operation. The keyless entry keypad is illuminated for 5 seconds when any button is touched. 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 (with stepped unlock enabled)
- Unlocks all doors
- Arms/disarms the perimeter alarm
- Releases the luggage compartment lid latch
- Activates the memory positions
- Enables/disables the autolock feature
- Enables/disables the auto-unlock feature

Field-Effect Transistor (FET) Protection

The SJB utilizes a Field-Effect Transistor (FET) protective circuit strategy for many of its outputs (for example, a 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 the fault event and a cumulative counter is started.

When the demand for the output is no longer present, the module resets the FET circuit protection to allow the circuit to function. The next time the driver requests a circuit to activate that has been shut down by a previous short (FET protection) and the circuit remains shorted, the FET protection shuts off the circuit again and the cumulative counter advances.

When the excessive circuit load occurs often 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 based on the harmful effect of each circuit fault on the FET and the ability of the FET to withstand it. A module lifetime level of fault events is established based upon the durability of the FET. If the total tolerance level is determined to be 600 fault events, the 3 predefined levels would be 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 automatically 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 module on-demand self-test, then the Clear DTC operation on the scan tool (if the on-demand test shows the fault corrected). The module never resets the fault event counter to zero and continues to advance the fault event counter as short circuit fault events occur.

If the number of short circuit fault events reach 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 only SJB FET protected output circuit for the handles, locks, latches and entry systems is the keypad illumination circuit CPK28 (WH/GN).