When I start the car and put it into drive the horn goes on, when I shut the car off the horn sounds! wont go off until I disconnect the battery

Sounds like a bad horn button which is actually part of the airbag. Replace your airbag. They're cheap on e-bay and it's not hard to do. Just make sure you disconnect the battery before doing any airbag work.

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.

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

Faulty horn switch in steering wheel?

You could also just unplug the horn, should only have one or two wires going to it. Then you could still drive the vehicle without that damn embarrassing horn randomly blowing. Hard to say , not knowing! ;-) I hope this helps.

sounds like you have an aftermarket alarm on your vehicle and the horn is disconnected

I am assuming you are not the original owner

sounds like the horn contact terminal inside the steering wheel got disconnected and is hitting a metal part of the steering column which triggers the horn. the terminal that got disconnected is probably has positive polarity and the metal part of the steering column has negative polarity. If they come in contact with each other... *honk* *honk*

I've had this exact problem before when being jumped off. The fob DOES NOT make it stop. We removed the fuse that goes to the horn. As soon as your battery gets recharged from the alternator, the fob will work again and the alarm will quit sounding. The only pain about removing the fuse is that the cruise control will not work until you put it back.

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.