I disconnected the battery when I reconnected the battery the alarm keeps going off

PATS does not blow the horn. Pull the horn fuse to see if that stops the draw. Then troubleshoot the horn circuit to see where the power is coming from. You can start at the horn relay. The relay gets a ground signal from the horn switch in the steering wheel. If that signal is constant, the problem is upstream of the relay--perhaps within the steering wheel. Do not remove the steering wheel to troubleshoot without disarming the airbag.

On some models you can disable the alarm after you connect the battery by locking and unlocking the driver door with the key.
I would disconnect the horn or pull the relay until you can get the alarm turned off.

Here's some info as it sound like the theft deterrent is armed.

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Reset Procedure

NOTE: This information applies to a Vehicle Theft Security System (VTSS) that was armed when the battery was disconnected and reconnected.

When the armed VTSS senses that the battery has been disconnected and reconnected, it enters its power-up mode. In the power-up mode the alarm system remains armed following a battery failure or disconnect. If the VTSS was armed prior to a battery disconnect or failure, the system will have to be actively or passively disarmed following a battery reconnection.

The power-up mode will also apply if the battery goes dead while the system is armed and battery jump-starting is attempted. The engine no-run feature will prevent the engine from starting until the alarm system has been actively or passively disarmed.

Passive disarming of the Vehicle Theft Security System (VTSS) occurs when the vehicle is unlocked using the key to unlock either front door or the liftgate. Active disarming of the VTSS occurs when the vehicle is unlocked by depressing the Unlock button of the Remote Keyless Entry (RKE) transmitter.

Once the alarm has been activated (horn sounding, lights flashing, and the engine no-run feature), either disarming method will deactivate the alarm.

Depressing the Panic button (if equipped) on the RKE transmitter will also disarm the VTSS, but the horn will sound and the lights will flash for about three minutes as part of the Panic feature. The horn and lights can be stopped by pressing any of the RKE transmitter's buttons or driving the vehicle above 15 mph.

The alarm system somehow got activated , this is usually because the battery becomes discharged or disconnected try doing this:
Remove the key from the ignition
disconnect the negative battery terminal
put the key back in and turn to ON
exit the truck and leave door open
reconnect the battery terminal
get in and leave door open, if the alarm horn stays off it should start.

take out the alarm fuse! :D

factory security does not have toggle switches as far as I know so it is probably an aftermarket system. Try one of two things, turn the toggle switch the oposite direction with battery disconnected. Reconnect the battery and try again, the horn will beep a few times when you reconnect. try starting. If that doesn't work, disconnect the battery and turn the key to the on position and reconnect the battery and the horn will sound but will go off get in the car and try to start. It should start and run normally. shut car off, then you should be able to return the toggle switch to the previous position If this happens again turn the toggle switch to the opposite position with the batterry disconnected and turn the key switch to the on position and reconnect the battery and start when started go see a service that installs aftermarket systems and they should be able to reset it security system Hope this helps

Disconnecting the car battery will reset the alarm system. When you first connect the car battery, the alarm will sound briefly, then stop. You will have to retrain the alarm system to recognize your remotes. The procedure for that varies from one year model to the other. On my 1998 you do it by putting the key in the door lock and holding it full counterclockwise until you hear a brief beep from the alarm horn. Then press a button on your remote and the system will learn to recognize that remote.

try to put the key in the ingnition and turn it to the on possition and walk away for about 15 min come back turn it to off and see iff it starts

Jerome, look for the blast horn see if can can determine which wire is power and disconnect it, should be silent then, you will have to disable the alarm once power is restored, then reconnect and reset if desired.

Alarm Module Reset Procedure
NOTE: This information applies to a Vehicle Theft Security System (VTSS) that was armed when the battery was disconnected and reconnected.
When the armed VTSS senses that the battery has been disconnected and reconnected, it enters its power-up mode. In the power-up mode the alarm system remains armed following a battery failure or disconnect. If the VTSS was armed prior to a battery disconnect or failure, the system will have to be actively or passively disarmed following a battery reconnection.
The power-up mode will also apply if the battery goes dead while the system is armed and battery jump-starting is attempted. The engine no-run feature will prevent the engine from starting until the alarm system has been actively or passively disarmed.
Passive disarming of the Vehicle Theft Security System (VTSS) occurs when the vehicle is unlocked using the key to unlock either front door or the lift gate. Active disarming of the VTSS occurs when the vehicle is unlocked by depressing the Unlock button of the Remote Keyless Entry (RKE) transmitter.
Once the alarm has been activated (horn sounding, lights flashing, and the engine no-run feature), either disarming method will deactivate the alarm.
Depressing the Panic button (if equipped) on the RKE transmitter will also disarm the VTSS, but the horn will sound and the lights will flash for about three minutes as part of the Panic feature. The horn and lights can be stopped by pressing any of the RKE transmitter's buttons or driving the vehicle above 15 mph.