Principles of Operation

Steering Column Switches

Principles of Operation

Ignition Switch

When the ignition lock cylinder is turned using the key, a mechanical connection positions the ignition switch to the desired position. The available ignition switch positions are:

- OFF
- ACC
- RUN
- START

When placed in any position other than OFF, the ignition switch provides fused battery voltage inputs to the Body Control Module (BCM). When placed in the START position, the ignition switch also provides fused battery voltage input to the PCM. The ignition switch contains a key-in-ignition input that allows the BCM 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 for the brake shift interlock system. For information on the brake shift interlock system, refer to Automatic Transaxle/Transmission External Controls Testing and Inspection.

Key Removal Inhibit Solenoid

The key removal inhibit solenoid (also known as the key release interlock actuator) is an electronically controlled solenoid that prevents the ignition lock cylinder from being turned to the OFF position unless the gear selector lever is in the PARK position. The key removal inhibit solenoid is part of the ignition switch.

Steering Column Control Module (SCCM)

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

- Wiper and washer system, refer to Wipers and Washers Testing and Inspection.
- Exterior lighting, refer to Exterior Lighting Testing and Inspection.
- Interior lighting, refer to Interior Lighting Testing and Inspection.
- Steering wheel audio controls (if equipped), refer to Information and Entertainment Systems Testing and Inspection.
- Steering wheel message center controls (if equipped), refer to Instrumentation, Message Center, and Warning Chimes Testing and Inspection.
- Cruise control, refer to Cruise Control Testing and Inspection.
- Adjustable pedals, refer to Hydraulic Brake Actuation Testing and Inspection.
- Steering column control, refer to Steering Column Testing and Inspection.

The SCCM also provides a pass-through circuit path for various components and/or features:

- Steering wheel switch illumination
- Driver air bag module
- Horn

The multifunction switch, brake pedal control switch (if equipped), hazard flasher switch, steering column control switch (if equipped), and LH/RH steering wheel switches (if equipped) provide inputs to the SCCM. Based on inputs from the various switches, the SCCM communicates over the High Speed Controller Area Network (HS-CAN) or the Local Interconnect Network (LIN) to control the supporting features.

Clockspring

The clockspring is mounted on the front of the SCCM and provides a continuous electrical connection between the driver air bag and the Restraints Control Module (RCM) when the steering wheel is turned. For information on the clockspring and other components of the Supplemental Restraint System (SRS), refer to Supplemental Restraint System Air Bag Systems.

Steering Wheel Rotation Sensor

The steering wheel rotation sensor is mounted on the front of the SCCM behind the clockspring and provides steering wheel position information to the SCCM. This information is broadcast over the HS-CAN.

Multifunction Switch

The multifunction switch is mounted directly to the SCCM and controls the low/high-beam headlamps, flash-to-pass, turn signals, windshield wiper by transferring the driver inputs to the SCCM. The high-beam headlamps, flash-to-pass and turn signals are communicated from the SCCM over the HS-CAN and the windshield wiper signals are communicated from the SCCM to the wiper motor internal module over the LIN. When the BCM receives the correct signal from the SCCM, the BCM activates the required component.

Brake Pedal Control Switch

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

Hazard Flasher Switch

The hazard flasher switch is mounted directly to the SCCM 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 to the BCM. When the ground signal is sensed by the BCM 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. Depending on what features the vehicle is equipped with, the SCCM sends messages via the HS-CAN to the PCM (cruise control), Instrument Panel Cluster (IPC) (message center) and BCM (entertainment system). The SCCM entertainment system messages are received by the BCM via HS-CAN and gatewayed over the Medium Speed Controller Area Network (MS-CAN) where the messages are received by the applicable entertainment system module(s).