Commander 4WD V8-4.7L VIN N (2006)
Steering Column Lock: Description and Operation
SHAFT LOCK MODULE
DESCRIPTION
A shaft lock module (1) is part of the premium version of the Sentry Key Immobilizer System (SKIS) in the Vehicle Theft Security System (VTSS). The
premium version of the SKIS is only available in vehicles built for certain markets, where the additional features offered by this system are required. The
shaft lock module is located in a bracket integral to the lower end of the steering column housing casting below the instrument panel in the passenger
compartment. This unit is designed to work in conjunction with the Sentry Key REmote Entry Module (SKREEM) to control a locking bolt (2) that
engages a machined slot in the steering shaft to prevent shaft rotation whenever there is not a valid key present in the ignition lock cylinder on the
instrument panel.
The die cast aluminum shaft lock module housing has a series of integral engagement tabs and slide tabs that engage matching slots and channels integral
to the mounting bracket on the steering column. When the module is fully engaged in the mounting bracket, two spring clips (3) on the module engage
the bracket, locking the module securely into place. Concealed within the module is the electronic circuitry of the module, and a bi-directional electric
motor that actuates the locking bolt. The module is connected through an integral connector receptacle (4) to the vehicle electrical system through a take
out and connector of the instrument panel wire harness.
The mounting provisions for the shaft lock module are designed to resist unauthorized tampering. The module cannot be removed from the steering
column while the locking bolt is in the locked position, or while the steering column is installed in the vehicle. The shaft lock module unit cannot be
adjusted or repaired and, if ineffective or damaged, it must be replaced.
OPERATION
The electronic circuitry within the shaft lock module contains all of the logic circuits and components to monitor and control the operation of the shaft
locking bolt. The module uses a serial data bus for bi-directional communication with the Sentry Key REmote Entry Module (SKREEM). If the module
detects a problem with the positioning or operation of the locking bolt, it sends an error message to the SKREEM. The SKREEM then stores a
Diagnostic Trouble Code (DTC) and sends an electronic error message to the Electromechanical Instrument Cluster (EMIC) over the Controller Area
Network (CAN) data bus, and a SERVICE COLUMN LOCK textual message will appear in the instrument cluster dot matrix display.
The shaft lock module continuously monitors inputs from the SKREEM and energizes the electric motor to move the locking bolt to the locked or
unlocked position based upon that input. If the SKREEM indicates that the key present in the ignition lock cylinder is invalid, the locking bolt remains in
the locked position. When the SKREEM indicates that a valid key is present in the ignition lock cylinder, the shaft lock module operates a motor to move
the locking bolt to the unlocked position. However, to prevent inadvertent column locking due to a failure while the vehicle is being operated, the
module cannot move the locking bolt from the unlocked position to the locked position as long as a key remains in the ignition lock cylinder.
The shaft lock module receives ground at all times through a hard wired remote ground point. The module receives battery voltage to operate and to
move the locking bolt in the unlocked direction on a fused B(+) circuit through a fuse in the Junction Block (JB), and receives battery voltage to operate
the locking bolt in the locked direction only when the key is removed from the ignition switch. These connections allow the module to remain
operational, regardless of the ignition switch position.
For added system security, the shaft lock module learns a unique Secret Key code from the SKREEM over the serial data bus upon initialization. This
code is stored in the memory of the module and cannot be changed. Therefore, if the SKREEM requires service replacement, a new shaft lock module
will also be required. Another security code, called a PIN, is used to gain access to the SKREEM Secured Access Mode. The Secured Access Mode is
required during service to initialize a new shaft lock module.
