Steering Column: Description and Operation
Steering ColumnControl Diagram - Steering Column Adjustment - Without Memory
NOTE: A = Hardwired
Control Diagram - Steering Column Adjustment - Without Memory (Part 1):
Control Diagram - Steering Column Adjustment - Without Memory (Part 2):
Control Diagram - Steering Column Adjustment - With Memory
NOTE: A = Hardwired
Control Diagram - Steering Column Adjustment - With Memory (Part 1):
Control Diagram - Steering Column Adjustment - With Memory (Part 2):
Control Diagram - Column Lock
NOTE: A = Hardwired; B = K Bus; C = Diagnostic DS2 Bus
Control Diagram - Column Lock (Part 1):
Control Diagram - Column Lock (Part 2):
Steering Control Diagram - Steering Wheel Heating
NOTE: A = Hardwired
Steering Control Diagram - Steering Wheel Heating (Part 1):
Steering Control Diagram - Steering Wheel Heating (Part 2):
Steering Column
Steering Column (Part 1):
Steering Column (Part 2):
The steering column features fully electrical adjustment for tilt and reach. On vehicles fitted with memory seats, the steering wheel position control is incorporated into the memory seat module.
The column also features an electronically controlled steering lock. The lock is operated when the ignition switch senses that the correct key has been inserted. A control module, located inside the steering column, controls a motor operated lock, releasing the steering lock when appropriate.
The steering column comprises the upper column assembly which is connected to the steering rack via several shafts which are connected via a flexible coupling and universal joints.
The lower column comprises upper and lower shafts which are connected together as a sliding fit. The sliding fit allows the shafts to collapse in the event of a frontal collision, preventing column intrusion into the vehicle interior. The upper shaft is connected to a flexible coupling and provides the attachment to the upper column. The lower shaft has internal splines which connect with splines on the steering rack valve input shaft. The upper shaft is fitted with a white colored sealing ring and a gaiter.
The upper column also comprises two shafts which are also connected together as a sliding fit. The shafts are a double 'D' section to prevent rotation. The sliding fit allows the shafts to collapse in the event of a frontal collision further preventing intrusion into the vehicle interior. The lower shaft is connected to the flexible coupling which transfers torque to the lower column and the steering rack. The upper shaft has a splined internal bore which connects with the adjustable upper column assembly.
The upper column assembly comprises two extruded aluminum sections which connect together and can slide on each other in the event of a frontal impact, further preventing column intrusion into the vehicle interior. The column is attached to the cross-car tube with four bolts. Two straps are bolted to the upper of the two aluminum sections. The straps are coiled around a bush on the upper section and have a hook which locates on the lower section. In the event of a frontal impact, the straps can unwind, allowing the upper column to collapse in a controlled manner absorbing energy.
The upper column also provides the location for the steering angle sensor which is used by the Dynamic Stability Control (DSC) system.
The upper column provides the locations for the column adjustment motors and the steering lock mechanism and steering lock control module. The steering lock operates via a locking bolt which engages with a locking sleeve located around the column shaft. The locking sleeve has a tolerance ring which is located between the sleeve and the column. The tolerance ring allows the locking sleeve to slip on the upper column shaft if a high torque is applied to the steering wheel when the lock is engaged. This prevents the locking bolt from being sheared by someone forcibly turning the steering wheel while the steering lock is engaged, yet still effectively locking the steering.
Column Adjustment
Column Adjustment (Part 1):
Column Adjustment (Part 2):
The steering column is adjusted using a four way switch located on the LH (left-hand) side of the steering column, below the LH (left-hand) column switch.
The steering column adjustment is achieved by two electric motors and a column adjustment control unit on vehicles without memory seats or by the memory seat module on vehicles with memory seats. Both motors are attached to the lock housing / tilt head assembly and move the column via worm drive screws.
The reach adjustment motor drives a screw shaft which moves the column in and out for reach adjustment. The adjustment is achieved by the two extruded aluminum sections which slide on one another. The tilt adjustment motor also drives a screw shaft. This shaft is connected to a cam, which causes the tilt head to pivot, adjusting the column angle.
On vehicles without memory seats, inputs from the column adjustment switch are received by the adjustment control unit located under the column. The control unit interprets the signals from the switch and operates the requested adjustment motor in the required direction.
On vehicles with memory seats, the adjustment control unit is not fitted. Inputs from the column adjustment switch are received by the memory seat module which is incorporated into the driver's seat switch pack. The module interprets the signals from the switch and operates the requested adjustment motor in the required direction. The motors used on the memory vehicles have Hall effect sensors known as 'ripple counters'. These counters output the position of the column when the seat memory store function is used and applies this setting to the applicable ignition key.
Electronic Steering Column Lock
With the ignition switch located in the center console, a conventional steering lock mechanism cannot be used. An electronic system was designed which comprises an ignition switch assembly with a position switch and anti-rotational lock and a steering column assembly locking unit with integrated steering lock control module.
The upper steering column assembly houses the column lock mechanism and control module. The components are assembled with non-removable pins for security reasons and are therefore non-serviceable. Failure of any steering lock components will require replacement of the upper steering column assembly.
Steering Lock
Steering Lock (Part 1):
Steering Lock (Part 2):
The steering column lock comprises a locking motor, locking bolt and a safety release solenoid actuator. The actuator is required to hold the locking bolt in the unlocked position in the event of power loss during operation. The locking motor drives a cam which moves the locking bolt into and out of engagement with the locking sleeve on the steering column. The locking motor is fitted with a Hall effect sensor which informs the steering lock control module of the position (locked/unlocked) of the steering lock mechanism.
Steering Lock Control Module Harness Connector
Steering Lock Control Module Harness Connector:
Steering Lock Control Module Harness Connector C2055 Pin Details
Steering Lock Control Module Harness Connector C2055 Pin Details:
Ignition Switch and Locking Mechanism
Ignition Switch and Locking Mechanism (Part 1):
Ignition Switch and Locking Mechanism (Part 2):
The ignition switch assembly also has a locking mechanism which works in conjunction with the immobilization control module and the steering lock control module. The ignition switch mechanism comprises an ignition switch lock solenoid actuator which prevents the ignition switch being rotated unless the key has been recognized by the immobilization control module. A Hall sensor is located in the ignition switch body and senses the rotation of the ignition switch. This signal is transmitted on the K bus and is used by the steering lock control module to confirm the key status with the immobilization control module.
Ignition Switch Lock Harness Connector
Ignition Switch Lock Harness Connector:
Ignition Switch Lock Harness Connector C0672 Pin Details
Ignition Switch Lock Harness Connector C0672 Pin Details:
Steering Lock Control Module Operation
The steering lock control module operates in conjunction with the immobilization control module and the ignition switch.
Detection of Unlock Request
When a 'valid' key is inserted in the ignition switch, the immobilization control module transmits a 'valid key in lock' message on the K Bus. The steering lock control module receives this message and starts the unlocking process of operating the steering lock motor to disengage the locking bolt.
The immobilization control module goes into sleep mode 60 seconds after the vehicle is unlocked and a key is not inserted in the ignition switch. When the key is subsequently inserted in the ignition switch and rotated, the rotation is sensed by the Hall rotation sensor in the switch. Further rotation is prevented by the ignition switch lock solenoid actuator. The rotation sensor transmits a signal which is received by the steering lock control module. This control module sends a 'request immobilization control module status' message on the K bus which wakes the immobilization control module. When the immobilization control module confirms that a valid key is inserted, the ignition switch lock disengages and the steering lock control module starts the unlocking process.
If the K bus is inoperative, the unlocking operation is initiated by the rotation sensor signal. This is indicated to the driver through a delayed operation of the solenoid actuator preventing the key from being turned initially. The solenoid actuator is operated on a delay which will initially prevent the key from being turned. The solenoid actuator will unlock and allow the key to turn on the second attempt. A defect in the K bus is detected if no response from the immobilization control module is received after a 2.4 seconds period after the 'request immobilization control module status' is sent.
Unlocking of Steering Lock
If the battery voltage is 9 V or less, the steering lock will be inoperative.
When a valid key is inserted and confirmed, the steering lock control module activates the steering lock motor in the unlock direction. Movement from the locked to the unlocked position is detected by the Hall sensor in the motor and sensed by the steering lock control module.
When the Hall sensor detects that the unlocked position has been reached, the control module brakes the motor. The safety release solenoid actuator is de-energized and its spring loaded pin drops into a recess in the locking bolt. This forms a mechanical lock securing the locking bolt in the unlocked position preventing the steering lock from being applied when the vehicle is being operated. A Hall sensor in the safety release solenoid actuator informs the steering lock control module of this condition. Once the unlocking procedure is successfully performed, the steering lock control module deenergizes the steering lock motor.
Once the steering is successfully unlocked, the ignition switch lock disengages allowing the key to be turned to positions II and III.
Detection of Locking Request
When the ignition key is turned to position 0, the ignition switch lock solenoid actuator remains active (unlocked) for 16 minutes. This function allows immediate restarting of the vehicle as long as the key is not removed from the ignition switch. When the key is removed, the immobilization control module senses the removal and transmits a 'no valid key in lock' message on the K bus. The steering lock control module checks that the ignition switch position 'II' or 'III' outputs and the rotation sensor are not active and initiates the steering locking process. This check ensures that the steering is not locked when the vehicle may be being driven.
If the K bus is inoperative, locking of the steering column is prevented by the steering lock control module. This is indicated to the driver when attempting to start the vehicle through a delayed operation of the ignition switch lock solenoid actuator preventing the key from being turned initially. The solenoid actuator is operated on a delay which will initially prevent the key from being turned. The solenoid actuator will unlock and allow the key to turn on the second attempt. A defect in the K bus is detected if no response from the immobilization control module is received after a 2.4 seconds period after the 'request immobilization control module status' is sent.
Locking of Steering Lock
The battery voltage must be greater than 10 V and the vehicle must be stationary.
The ABS (anti-lock brake system) module transmits vehicle speed on a hardwired connection with the steering lock control module. The steering lock control module uses the signal to determine when the vehicle has stopped.
When the key is removed and the steering lock control module receives the 'no valid key in lock' message from the immobilization control module, the steering lock motor is activated. The safety release solenoid actuator in the steering column is energized, withdrawing the pin from the locking bolt. The Hall sensor in the solenoid actuator informs the steering lock control module that the lock is released.
The steering lock control module then operates the steering lock motor in the lock direction. Movement from the unlocked to the locked position is detected by the Hall sensor in the motor and sensed by the steering lock control module. The safety release solenoid actuator is de-energized and rests on the locking bolt.