Steering Column Switches
Steering Column Switches
Principles of Operation
Ignition Switch
The ignition switch is controlled by the ignition lock cylinder and key. The ignition lock cylinder and ignition switch are connected mechanically, turning the lock cylinder places the switch into 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 voltage inputs to the Body Control Module (BCM). When placed in the START position, the ignition switch also provides a voltage input to the PCM. The BCM (Body Control Module) distributes this voltage to other modules and vehicle systems through the run/start bus. The microprocessor internal to the BCM (Body Control Module) broadcasts an ignition mode network message over the Medium Speed Controller Area Network (MS-CAN) and High Speed Controller Area Network (HS-CAN).
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 SCCM (Steering Column Control Module) controls the following systems and/or features:
- Wiper and washer system; for additional information, refer to Wiper and Washer Systems
- Exterior lighting; for additional information, refer to Lighting and Horns.
- Interior lighting; for additional information, refer to Lighting and Horns.
- Steering wheel audio controls (if equipped); for additional information, refer to Accessories and Optional Equipment
- Steering wheel message center controls (if equipped); for additional information, refer to Instrument Panel, Gauges and Warning Indicators
- Cruise control; for additional information, refer to Fire Suppression System
The SCCM (Steering Column Control Module) provides a pass-through circuit path for various components and/or features:
- Driver air bag module
- Heated Steering Wheel Module (HSWM)
- Horn
- Paddle shifters
- Steering wheel switch illumination
The multifunction switch, wiper/washer switch and steering wheel controls (if equipped) provide inputs to the SCCM (Steering Column Control Module). Based on input from these switches, the SCCM (Steering Column Control Module) communicates over the High Speed Controller Area Network (HS-CAN) to control the supporting features.
Clockspring
The clockspring is mounted on the front of the Steering Column Control Module (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 additional information on the clockspring and other components of the supplemental restraints system, refer to Restraints and Safety Systems &/or Air Bag Systems.
Multifunction Switch and Wiper/Washer Switch
The multifunction switch and wiper/washer switches are mounted directly to the Steering Column Control Module (SCCM) and transfer driver inputs to the SCCM (Steering Column Control Module). The multifunction switch controls turn signal, headlamp low/high beam and headlamp dimmer/flash-to-pass while the wiper/washer switch controls the front windshield wipers/washers and (if equipped) the rear window wiper/washer. The SCCM (Steering Column Control Module) receives the switch information as ground or voltage inputs then sends messages on the High Speed Controller Area Network (HS-CAN) or the Local Interconnect Network (LIN) to the appropriate module.
The high beam headlamps and flash-to-pass messages are sent to the Body Control Module (BCM) over the HS-CAN (High Speed Controller Area Network).
The turn signal messages are sent to the BCM (Body Control Module), Instrument Panel Cluster (IPC), Parking Aid Module (PAM) (if equipped) and Cruise-Control Module (C-CM) (if equipped) over the HS-CAN (High Speed Controller Area Network).
The windshield wiper messages are sent to the wiper motor internal module over the LIN (Local Interconnect Network).
Steering Wheel Controls
The steering wheel controls are mounted directly to the steering wheel and wired to the Steering Column Control Module (SCCM). Depending on what features the vehicle is equipped with, the SCCM (Steering Column Control Module) sends messages via the High Speed Controller Area Network (HS-CAN) to the PCM (cruise control) and the Instrument Panel Cluster (IPC) (message center and entertainment system). The IPC (Instrument Panel Cluster) receives the SCCM (Steering Column Control Module) entertainment system messages via the HS-CAN (High Speed Controller Area Network) and then sends them to the applicable entertainment system module(s) along the Infotainment Controller Area Network (I-CAN).
Steering Wheel Rotation Sensor
The steering wheel rotation sensor is mounted on the front of the Steering Column Control Module (SCCM) behind the clockspring and provides steering wheel position information to the SCCM (Steering Column Control Module). This information is broadcast over the High Speed Controller Area Network (HS-CAN).
Push Button Start System
The push button start system uses the following components to achieve the 4 ignition modes:
- Body Control Module (BCM)
- Brake Pedal Position (BPP)
- Intelligent Access (IA) key
- Remote Function Actuator (RFA) module
- Start/stop switch
The start/stop switch is a dual contact, normally open switch. The start/stop switch uses 2 sets of internal contacts for redundancy. The contacts are closed when the switch is pressed. The start/stop switch also has 2 LEDs, one LED is used for switch illumination and the other is used to indicate ignition mode. The mode indicator LED only illuminates when the vehicle is in RUN or START mode, it does not illuminate in ACC mode.
To achieve any ignition mode other than OFF, the IA (Intelligent Access) key must be present inside the vehicle. The driver need not perform any actions on the IA (Intelligent Access) key to operate the push button start system. It is sufficient that the IA (Intelligent Access) key is located inside the vehicle when the start/stop switch is pressed. Pressing the start/stop switch triggers radio frequency communication between the IA (Intelligent Access) key and the RFA (Remote Function Actuator) module. If the IA (Intelligent Access) key is not present when the start/stop switch is pressed, the push button start system will not transition from OFF mode and NO KEY DETECTED will be displayed in the message center.
Once communication between the IA (Intelligent Access) key and the RFA (Remote Function Actuator) module is established, the RFA (Remote Function Actuator) module sends a message over the Medium Speed Controller Area Network (MS-CAN) to the BCM (Body Control Module) indicating the correct IA (Intelligent Access) key is present. The BCM (Body Control Module) then takes the appropriate action based on the start/stop switch and BPP (Brake Pedal Position) switch inputs.
Backup Antenna
If the battery inside the IA (Intelligent Access) key is weak, damaged or if excessive ambient Radio Frequency Interference (RFI) prevents communication between the RFA (Remote Function Actuator) module and the IA (Intelligent Access) key, the backup antenna located in the glove box provides a secondary means for the RFA (Remote Function Actuator) module to validate the IA (Intelligent Access) key and authorize use of the vehicle. The backup antenna uses passive radio frequency identification to exchange signals with the IA (Intelligent Access) key, similar to the way a encoded Passive Anti-Theft System (PATS) key and transceiver operate. For information on the IA (Intelligent Access) key and backup antenna, refer to Antitheft and Alarm Systems.
Push Button Start System Message Center Messages
The message center provides instruction for operating the push button start system. The message center also displays warnings that indicate a potential concern with the push button start system. The following messages pertain to the push buttons start system:
- PRESS BRAKE TO START- Momentarily displays when the start/stop switch is pressed without the brake pedal being applied.
- ACCESSORY POWER ACTIVE- Displays when the vehicle is in ACC mode.
- SHIFT TO PARK- Displays when the start/stop switch is pressed to shut off the engine with the gear selector lever not in PARK.
- RESTART NOW OR KEY IS NEEDED- Displays when the start/stop switch is pressed to shut the engine off and the IA (Intelligent Access) key is not detected by the RFA (Remote Function Actuator) module.
- NO KEY DETECTED- Displays if the IA (Intelligent Access) key is not detected by the RFA (Remote Function Actuator) module while attempting to start the vehicle, enter ACC or RUN mode. If this message is observed with the IA (Intelligent Access) key located inside the vehicle, go to Antitheft and Alarm Systems to diagnose the IA (Intelligent Access) key.
- STARTING SYSTEM FAULT- Displays if the RFA (Remote Function Actuator) module receives invalid data from the PCM during PATS (Passive Anti-Theft System) authentication. If this message is observed, refer to Antitheft and Alarm Systems to diagnose the PATS (Passive Anti-Theft System) concern.
Remote Function Actuator (RFA) Module Programming
If it is necessary to replace the RFA (Remote Function Actuator) module, the replacement module must be programmed. Carry out the following scan tool functions if a new RFA (Remote Function Actuator) module is installed:
NOTE: All of the following scan tool functions must be completed before the vehicle will start.
- Programmable Module Installation (PMI)- This process configures the new module with specific vehicle information. Refer to Programmable Module Installation (PMI) in Information Bus Programmable Module Installation (PMI).
- PATS (Passive Anti-Theft System) Parameter Reset- This process initiates an exchange of information between the RFA (Remote Function Actuator) module and the PCM specific to the anti-theft/engine immobilizer feature. Refer to Passive Anti-Theft System (PATS) Parameter Reset-Intelligent Access (IA) in Antitheft and Alarm Systems Passive Anti-Theft System (PATS).
- IA (Intelligent Access) Key Programming- This process programs the IA (Intelligent Access) keys to the RFA (Remote Function Actuator). Refer to Key Programming Using Diagnostic Equipment-Intelligent Access (IA) in Antitheft and Alarm Systems Key Programming Using Diagnostic Equipment.