Steering Wheel and Column Description and Operation

Steering Wheel and Column Description and Operation

Tilt/Telescoping Switch Operation
The tilt/telescoping steering column has a four-position switch which may be used to adjust the position of the steering wheel in or out which is telescope and up or down which is tilt. The position of the column may be changed as follows:
^ Press the switch up to tilt the column up.
^ Press the switch down to tilt the column down.
^ Press the switch forward and the column moves toward the front of the vehicle.
^ Press the switch rearward and the column moves toward the rear of the vehicle.

The steering column module (SCM) receives inputs from the tilt/telescope switch to manually move the column to a desired position. Pressing the control switch sends an input to the SCM. The SCM receives an input and actuates the corresponding column motor.

Pressing the switch momentarily in either the UP or DOWN, or IN or OUT position, and releasing within 0.5 seconds, causes the column to advance slightly in the corresponding direction then stop. This feature allows fine control of the steering column position in each direction. If the switch is pressed and held for longer than 0.5 seconds, the column advances slightly in that direction, pauses, then resumes movement as long as the switch is held.

Motors
Both the tilt and telescoping motors are reversible. For example, the tilt motor moves the column both up and down. When the SCM receives an input to move the column up, the SCM supplies battery positive voltage and ground to the tilt motor in order to move the column up. When the SCM receives a column down input, the SCM supplies battery positive voltage and ground to the same motor, but with a reverse polarity. When the voltage polarity is reversed, the motor runs in the opposite direction and moves the column down.

Position Sensors
Two position sensors are used by the SCM to store column positions in memory and to return the column to the stored memory positions. The SCM provides a 5-volt reference voltage and a ground to both the tilt and telescoping position sensors. The sensor feedback circuit voltage varies from 0.25-4.75 volts. Each sensor is mounted to its corresponding motor cable assembly. When the motor rotates its cable, the resistance of the sensor varies. The SCM monitors the feedback voltage to determine the column position via the tilt and telescoping position sensor input circuits. When an entry or exit position is saved, the SCM stores the column positions by recording each position sensor's feedback voltage. When an entry or exit position is commanded, the module moves the motors until all the position sensor feedback voltages equal the feedback voltages stored in memory.

Tilt/Telescoping Memory
Memory settings and the personalization of steering wheel positions are available with the tilt/telescoping steering column. The data stored consists of entry positions and exit positions. The entry position is the position that the steering column moves in when the ignition is turned ON. The exit position is the direction that the steering column moves in when the ignition is turned OFF and the driver's door is opened.

An initial memory setting is set in the SCM at the assembly plant. This setting may be changed to suit the customer at the time of purchase or at anytime in the future.

Entry/Exit Personalization
The SCM stores personalization information. The driver information center (DIC) is used to enable and disable the personalization feature in the SCM. A Class 2 message is sent to the SCM, by the DIC, which specifies that the SCM enable the personalization feature until disabled again using the DIC.

The steering column control module can store 6 possible positions: 3 entry positions and 3 exit positions.
^ Driver 1 exit position, set using the memory switches
^ Driver 2 exit position, set using the memory switches
^ Default exit position which is all forward, all up, with no memory position set
^ Driver 1 entry position, set using the memory switches
^ Driver 2 entry position, set using the memory switches
^ Last known driver entry position which is when the ignition is turned ON by an unknown driver

Memory Setting
When the driver door switch assembly (DDSA) receives inputs from the memory function switch, the steering column personalization positions may be recorded for one or two different drivers. Once a steering column driving entry or exit position is adjusted by the driver it must be set in memory. To record a position, the driver must press the SET MEMORY button, which is followed by a chime to acknowledge that input. Within 5 seconds, either the MEMORY 1 or MEMORY 2 button must be pressed. When the DDM receives these inputs, it sends a class 2 message to the SCM. The SCM records the feedback voltages from the column position sensors for that driver. A single chime is sounded to acknowledge that the position was recorded.

To record a second position, the second driver must press the SET MEMORY 2 button, after they have made the appropriate adjustments, and the process continued.

Memory Personalization Recall
When the driver presses the MEMORY 1 or MEMORY 2 button, the DDSA receives the input and a single chime is sounded. The DDSA sends a class 2 message to the SCM indicating which driver memory setting has been selected. The SCM applies both battery positive voltage and ground to the column motors until all the column position sensor feedback voltages equal the feedback voltages stored in memory for the appropriate driver.

When a keyless entry transmitter is used to unlock the vehicle doors, the remote function actuator (RFA) module communicates which driver key fob performed that command. The SCM receives the unlock command via a class 2 message from the RFA module.

Tilt/Telescoping Description
The energy absorbing and locking steering column includes three important features in addition to the steering function.
1. The steering column is energy absorbing and is designed to compress in a front-end collision which will lessen the chance of injury to the driver.
2. The steering column has a tilt/telescoping control system that consists of an electronic control module capable of class 2 serial data communication, a steering column power assembly with positioning motors and sensors, and a steering column control switch.
3. The multi-function lever provides for the control of the headlamp high beams, and the windshield washer and wiper.

Ignition Lock Cylinder Control Actuator (w/DTS)
If the vehicle is the DeVille Touring Sedan (DTS), it is equipped with a floor mounted console gear shifter, and has a ignition lock cylinder control actuator system in the steering column as an added safety feature. The ignition lock cylinder control actuator systems purpose is to prevent the steering wheel from being locked when the transmission is in gear and the vehicle may still be moving. The ignition lock cylinder control actuator system consists of the rear integration module (RIM), the lock cylinder relay, and the ignition lock cylinder control actuator. The ignition lock cylinder control actuator contains a pin that is spring loaded out to mechanically prevent the ignition key cylinder from being turned to the lock position when vehicle speed is above 5 mph for 15 seconds and the transmission is not in the Park position. If vehicle power is lost, and/or the transmission is not in the Park position the operator will not be able to turn the ignition key to the lock position and will not be able to remove the ignition key from the column. For situations where the vehicle must be towed, the system can be overridden by pressing a release button that is reached through an access hole located on the under side of the steering column. First, remove the black plug covering the hole.

Heated Steering Wheel
The heated steering wheel system consists of a heated steering wheel, a heated steering wheel switch, and a steering wheel heat module. The heated steering wheel includes a non-serviceable heating element and temperature sensor. The heating element and sensor are located in the rim of the steering wheel. The heated steering wheel switch is located in the steering wheel switch bezel. The steering wheel heat module is located on the backside of the steering wheel center hub. When the switch is pressed, a signal is sent to the controller and the heated steering wheel is turned on. The system then remains on until the customer turns it off. The wheels normal operating temperature is 32°C (89.6°F). The wheel takes approximately 3 to 4 minutes to reach the normal operating temperature. The wheel will take longer to heat up if the vehicle temperature is below -21°C (-5.8°F). The built-in temperature sensor provides input to the controller to limit the temperature to the normal operating temperature. The wheel will not operate if the vehicle temperature is at or above 32°C (89.6°F).