What might be the reason my lights no longer flash when I unlock the doors?

Have the VEHICLE THEFT SECURITY SYSTEM checked out-

The Vehicle Theft Security System (VTSS) is designed to protect against whole vehicle theft. The system monitors vehicle doors, deck lid key cylinder, and ignition action for unauthorized operation. The alarm activates:

Sounding of the horn
Flashing of the park and tail lamps
Flashing of the headlamps
An engine kill feature (without SKIS)