Operation

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), sometimes referred to as the Wireless Control Module (WCM). If the module detects a problem with the positioning or operation of the locking bolt, it sends an error message to the SKREEM/WCM. The SKREEM/WCM then stores a Diagnostic Trouble Code (DTC) and sends an electronic error message to the ElectroMechanical Instrument Cluster (EMIC), sometimes referred to as the Cab Compartment Node (CCN), over the Controller Area Network (CAN) data bus, and a SERVICE COLUMN LOCK message will appear in the instrument cluster display.

The shaft lock module continuously monitors inputs from the SKREEM/WCM and energizes the electric motor to move the locking bolt to the locked or unlocked position based upon that input. If the SKREEM/WCM indicates that the key present in the ignition lock cylinder is invalid, the locking bolt remains in the locked position. When the SKREEM/WCM 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 B(+) circuit, 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/WCM 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/WCM 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/WCM Secured Access Mode. The Secured Access Mode is required during service to initialize a new shaft lock module. The shaft lock module must be installed if it is damaged or inoperative.

Use a diagnostic scan tool and refer to the appropriate diagnostic information to diagnose and test the system.