As we all know, in the world of automotive technology, things keep changing. In the aftermarket, we tend to feel these changes a little later than the OE dealers. That being the case, it's no surprise that it has been only recently that many technicians are feeling the sting and frustrations caused by OE anti-theft devices and vehicle theft deterrent systems, also known as VTD.

Many technicians have blamed a newly installed aftermarket replacement PCM for a no-start condition only to find out later that the vehicle in question was equipped with VTD. Lots of time, money and patience have been spent solving a problem that shouldn't have existed had the technician checked if the vehicle was equipped with VTD. When dealing with these vehicles, driveability repair procedures may require one more step to be taken before handing the keys back to the customer, and that is a VTD/Anti-theft Relearn procedure.

While each manufacturer has its own way of incorporating VTD into the various models, the concept of "password sharing" among computer control modules within the vehicle is pretty common across the board. This prevents an unauthorized start-up of the engine. In other words, if the proper ignition key is not used to start the vehicle, the vehicle will shut down and the engine will become immobilized for a certain duration of time, usually from four to 10 minutes. General Motors started using VTD systems in the mid '80s beg...