Principles of Operation
Steering Column Switches
Principles of Operation
Ignition Switch
NOTE: The Smart Junction Box (SJB) is also identified as the Generic Electronic Module (GEM).
The ignition switch is controlled by the ignition lock cylinder with a key. When the ignition lock cylinder is turned using the key, a mechanical connection positions the ignition switch to the selected position, and allows the ignition switch to send voltage to the Battery Junction Box (BJB) and the SJB. The ignition switch also contains a key-in-ignition system that allows the SJB to detect when the key has been inserted in the ignition switch. This information is used by the SJB for the brake shift interlock system. For information on the brake shift interlock system, refer to Automatic Transmission/Transaxle. The available ignition switch positions are:
- OFF
- ACC
- RUN
- START
Multifunction Switch
The multifunction switch controls the various components (high-beam headlamps, flash-to-pass, turn signal and windshield wiper) by grounding certain Smart Junction Box (SJB) circuits and wiper motor circuits. When the SJB detects the specific ground, it sends a voltage to the appropriate component to activate it. The SJB controls the high-beam headlamps, the flash-to-pass and the turn signals. The high-beam headlamp and the turn signal portion are normally open switches that close when activated. The flash-to-pass switch is a momentary contact switch that grounds the SJB high-beam headlamp circuit. The windshield wipe and wash functions are controlled directly by the multifunction switch, wiper and washer motor.
Circuit Deactivation Ignition Module (CDIM)
Vehicles equipped with a 6.4L engine may also be equipped with an extended idle shutdown system. The system is controlled by the PCM and uses several inputs to determine whether or not to shut the engine off. The function of the Circuit Deactivation Ignition Module (CDIM) is to disable the ignition circuits after the PCM has shut the engine off. For a complete description of the extended idle shutdown system and the related components, refer to Powertrain Control Software in Computers and Control Systems Information.
Once the PCM has determined that the engine should be shut down, it sends a message to the Instrument Cluster (IC) along the High Speed Controller Area Network (HS-CAN) bus. The IC then sends a message to the CDIM along the Medium Speed Controller Area Network (MS-CAN) bus. Once the CDIM receives the message from the IC, the CDIM will begin a 60 second timer and monitor the MS-CAN bus for ignition switch position, brake pedal position and engine rpm. If the rpm remains at 0 and both the ignition switch and brake pedal switch remain undisturbed for 60 seconds, all CDIM internal relays will open and the vehicle will enter into the standard accessory delay. If 1 or more of the monitored signals changes during the 60 second time period, the CDIM internal relays will remain closed and allow voltage to remain applied to the ignition circuits.
To reactivate the CDIM and ignition circuits after the engine shuts down and the 60 second time elapses, the ignition key must be turned to the OFF position before attempting to start the engine or before the key is turned to any other position.
If the vehicle is getting the extended idle shut down system and the CDIM installed at a dealership as opposed to the assembly plant, the PCM must be enabled. To enable the PCM for extended idle shutdown, refer to the Extended Idle Shutdown Initialization General Procedure in Computers and Control Systems.