SECURITY Indicator Flashes and Engine Does Not Start
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
The theft deterrent control module has measured an incorrect transponder value, the calculation to the challenge is incorrect or the PCM has lost communication with the theft deterrent control module, The VTD system considers this a tamper condition. The VTD indicator will flash.