Accepted Answer

Thanks for the question.

 

The reason the security lamp is coming on is due to a failure within the passlock system.

 

The ignition lock cylinder is located at the upper right side of the steering column. The Passlock^TM sensor is in the steering column. The Passlock^TM sensor is separate from the key and lock cylinder. The key and the lock cylinder work together in order to determine if the proper ignition key was used to start the vehicle.

In the event of an open Class 2 serial data line between the BCM and the VCM/PCM, the vehicle will become fail-enabled if the VCM/PCM has already received the password from the BCM for that ignition cycle, the engine is running. In this event, the following conditions occur:

•	The security telltale will be ON continuously.

•	The VCM/PCM will become fail-enabled for future ignition cycles.

 

The system will need to be scanned for body codes, which typically, only a GM dealer can do.

Expert:	Travis
Pos. Feedback:	99.0 %
Accepts:
Answered:	3/12/2009

Chevy Technician

7+ years of GM dealership experience, GM ASEP trained, Assoc. Degree in Auto. Tech.