Principles of Operation

Steering Column Switches

Principles of Operation

Ignition Switch

The ignition switch is controlled by the ignition lock cylinder and a key. The ignition lock cylinder and ignition switch are connected mechanically, turning the lock cylinder places the switch into the desired position. The available switch positions are:

- OFF

- ACC

- RUN

- START

When the lock cylinder is turned from the OFF position, the ignition switch provides voltage inputs to the Body Control Module (BCM), the PCM and the Brake Shift Interlock Actuator (BSIA) based on the specific position selected. The ignition switch contains a key-in-ignition input that allows the BCM (Body Control Module) to detect when the key has been inserted in the ignition, to initiate the module wake up cycle. This information is also used by the BCM (Body Control Module) for the brake shift interlock system. For information on the brake shift interlock system, refer to Automatic Transmission/Transaxle.

Steering Column Control Module (SCCM)

The SCCM (Steering Column Control Module) controls various systems and/or features:

- Wiper and washer system; refer to Wiper and Washer Systems.

- Exterior lighting; refer to Lighting and Horns.

- Interior lighting; refer to Lighting and Horns.

- Steering wheel audio controls (if equipped); refer to Accessories and Optional Equipment.

- Steering wheel message center controls (if equipped); refer to Instrument Panel, Gauges and Warning Indicators.

- Cruise control; refer to Fire Suppression System.

- Adjustable pedals; refer to Hydraulic System, Brakes &/or Brake Pedal Assy.

The SCCM (Steering Column Control Module) provides a pass-through circuit path for various components and/or features:

- Steering wheel switch illumination

- Driver air bag module

- Horn

The multifunction switch, adjustable pedal switch (if equipped), hazard flasher switch and steering wheel controls (if equipped) provide inputs to the SCCM (Steering Column Control Module). Based on inputs from the various switches, the SCCM (Steering Column Control Module) communicates over the High Speed Controller Area Network (HS-CAN) to control the supporting features.

Multifunction Switch

The multifunction switch is mounted directly to the SCCM (Steering Column Control Module) and controls the high beam headlamps, flash-to-pass, turn signals and windshield wiper by transferring the driver inputs to the SCCM (Steering Column Control Module). The high beam headlamps, flash-to-pass and turn signals are communicated from the SCCM (Steering Column Control Module) over the HS-CAN (High Speed Controller Area Network). The windshield wiper signals are communicated from the SCCM (Steering Column Control Module) to the wiper motor internal module over the Local Interconnect Network (LIN). The BCM (Body Control Module) activates the required components when the correct signal is received from the SCCM (Steering Column Control Module).

Adjustable Pedal Switch

The adjustable pedal switch is mounted directly to the SCCM (Steering Column Control Module) and controls the forward and rearward movement of the accelerator and brake pedals. The adjustable pedal switch functions when the ignition switch is in the OFF, ACC or RUN positions. When the adjustable pedal switch is pressed voltage is connected through the SCCM (Steering Column Control Module) to the adjustable pedal motor.

Hazard Flasher Switch

The hazard flasher switch is mounted directly to the SCCM (Steering Column Control Module) and operates when the ignition switch is in any position or when the key is removed. One press of the switch supplies a ground signal through the SCCM (Steering Column Control Module) to the BCM (Body Control Module). When the ground signal is sensed by the BCM (Body Control Module), it turns the directional indicators on. A second press of the button releases the ground connection and turns the directional indicators off.

Steering Wheel Switches

The steering wheel switches are mounted directly to the steering wheel and wired to the SCCM (Steering Column Control Module). Depending on what features the vehicle is equipped with, the SCCM (Steering Column Control Module) sends messages via the HS-CAN (High Speed Controller Area Network) to the PCM (cruise control), Instrument Panel Cluster (IPC) (message center) and BCM (Body Control Module) (entertainment system). The BCM (Body Control Module) receives the SCCM (Steering Column Control Module) entertainment system messages via the HS-CAN (High Speed Controller Area Network) and sends them over the Medium Speed Controller Area Network (MS-CAN), where the messages are received by the applicable entertainment system module(s).

Circuit Deactivation Ignition Module (CDIM)

Vehicles equipped with a 6.7L diesel engine may also be equipped with an extended idle shutdown system. This system is controlled by the PCM and uses several inputs to determine whether or not to shut the engine off. The CDIM (Circuit Deactivation Ignition Module) disables the ignition switch circuits after the PCM has shut the engine off. For a complete description of the extended idle shutdown system and related components, refer to Computers and Control Systems Information.

Once the PCM has determined that the engine should be shut down, it sends a message to the IPC (Instrument Panel Cluster) along the HS-CAN (High Speed Controller Area Network). The IPC (Instrument Panel Cluster) then sends a message to the CDIM (Circuit Deactivation Ignition Module) along the MS-CAN (Medium Speed Controller Area Network). Once the CDIM (Circuit Deactivation Ignition Module) receives the message from the IPC (Instrument Panel Cluster), the CDIM (Circuit Deactivation Ignition Module) begins a 60 second timer and monitors the MS-CAN (Medium Speed Controller Area Network) 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 (Circuit Deactivation Ignition Module) internal relays open and the vehicle enters into the standard accessory delay. If one or more of the monitored signals changes during the 60 second time period, the CDIM (Circuit Deactivation Ignition Module) internal relays remain closed, allowing voltage to remain applied to the ignition circuits.

To reactivate the CDIM (Circuit Deactivation Ignition Module) and ignition circuits after the engine shuts down, the ignition switch must be turned to the OFF position before attempting to start the engine or before the ignition switch is turned to any other position.

If the vehicle is getting the extended idle shut down system 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.