Module, Electronic Steering Lock (ESL): Operation

The shaft lock module (also known as the Electronic Steering Column Lock/ESCL or the Elektronische Lenkungs Verriegelung/ELV) is designed to work in conjunction with the ignition switch and the Sentry Key Immobilizer System (SKIS) to control a locking bolt that engages a machined slot in the steering shaft to prevent shaft rotation whenever the status of the ignition switch is Lock or the status of the Sentry Key transponder is an invalid key. The shaft lock module can only be unlocked when the presence of a valid Sentry Key transponder unit is detected and the status of the ignition switch is Run/Start.

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 the Controller Area Network (CAN) data bus for bi-directional communication with the SKIS circuitry within the Body Control Module (BCM). If the module detects a problem with the positioning or operation of the locking bolt, it sends an error message to the BCM. The BCM then sets and stores a Diagnostic Trouble Code (DTC) and sends an electronic error message over the CAN data bus to other electronic modules in the vehicle.

The shaft lock module continuously monitors inputs from the BCM and energizes the electric motor to move the locking bolt to the locked or unlocked position based upon that input. If the SKIS circuitry within the BCM indicates that the Sentry Key transponder present in the ignition lock cylinder is invalid, the locking bolt remains in the locked position. When the SKIS circuitry indicates that a valid Sentry Key transponder is present in the ignition lock cylinder and the status of the ignition switch is Run or Start, 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 the status of the ignition switch remains Run or Start.

The shaft lock module receives a path to 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 status of the ignition switch is Off and other data from the BCM allows it.

The hard wired circuits of the shaft lock module may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the shaft lock module or the electronic controls and communication between other modules and devices that provide some features of the SKIS. The most reliable, efficient and accurate means to diagnose the shaft lock module or the electronic controls and communication related to SKIS operation requires the use of a diagnostic scan tool.