Daughter has a 2000 GC. Car started to flash lights and blow horn, "panic" mode. This happens when she is driving and will not stop untill you disconnect the battery. Any idea where to start?

 

problem with the sentrykey antitheft system,

could just be a bad key(try another key)

 

Tried both keys and fobs on two different days

 

Could be door switches or the BCM, But here is some information.
REMOTE KEYLESS ENTRY (RKE) SYSTEM
DESCRIPTION

Key Fob Transmitter

The key fob transmitter has three buttons to actuate and program the Remote Keyless Entry (RKE) system.

OPERATION
UNLOCK : Pressing the UNLOCK button once will unlock the driver door and activate the illuminated entry system and disarm Vehicle Theft Security System, if equipped. Pressing the UNLOCK button twice within five seconds will unlock all doors and activate the illuminated entry system.
LOCK : Pressing the LOCK button locks all doors and sounds horn (chirp) and arm the Vehicle Theft Security System. The chirp verifies the door lock operation.
PANIC : Pressing the PANIC button sounds the horns at half second intervals, flashes the exterior lamps, and turns ON the interior lamps. The panic alarm will remain on for three minutes, or until the PANIC button is actuated again or the ignition switch is turned to the RUN position.
The Remote Keyless Entry Module is capable of retaining the transmitter Vehicle Access Code(s) (VAC) in its memory even after vehicle power has been interrupted.

The RKE system activates the optional memory seat and mirror system, if equipped. Two primary key fob transmitters can be programmed to actuate memory seat and mirror setting 1 or 2. Two additional key fob transmitters can be added, but they will not be able to operate the memory seat and mirror system.