A steering column lock is designed to deter thieves, since even if the car is started illegally, it cannot be driven properly with the steering column lock still engaged. Many vehicle manufacturers are producing models in which automatic steering column locks are standard equipment.
In the automatic version of a steering column lock, the system is controlled by the body control module, which incorporates electronic signals to sense whether the lock has been disengaged. When the key is inserted into the ignition and turned to the on position, a signal is immediately sent to the BCM, which then sends a signal to the electronic column lock, which disengages the steering column lock and allows the steering wheel to be used before the car is even started.
Locking mechanisms differ from car to car, but most include some type of bolt lock. When the system is off and the wheel is locked, the bolt is closed. When the ignition system is used properly, the bolt is electronically opened so that the wheel can be turned.
Some versions of steering column locks are manual in nature. These are usually wired into the transmission system, so that the transmission must be used to engage or disengage the lock. For instance, some systems require that the car be put into the park position before the ignition can be switched to the lock position.
There are also steering column locks available for outer installation. These fit around the steering wheel column and are designed to be noticeable so that thieves would be less willing to break into the car. Some of these are also keyed into the ignition system, while others include a separate locking function.
For automatic models, there are often bypasses available that disengage the lock at all times. This is done to avoid problems with the automatic locks. If a particular vehicle model has problems with locks becoming broken, then an owner might want to put in a bypass to avoid problems down the line. Steering-column locks can become permanently locked and require manufacturer repair if they malfunction.