Security alarm starts honking randomly when car is locked.

Put the key ignition to the ON switch for 15 minutes, when the light start blinking (or a beep sound goes on), turn the key to OFF, remove the key (you have to remove it) then start the car again. If it doesn't work, do the whole process for 30 minutes wait instead of 15 minutes. Good luck, there are video also for bypassing the passlock security in youtube.

The battery is most likely gone dead

Disconnect it & have it tested over the
next couple days

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

First, Have your Battery tested. The Alarm systems in Ford made Products are very sensitive to Voltage. There are 3 systems in the car which interrupt power, the Alarm system (horn honking) and the Battery saver and finally the starter interlock system.

The Alarm system will do several things to disable the car from starting. It will reduce the voltage to the starter to prevent the engine from turning over. Some will even kill the ignition system so that if the starter is jumped, the car still won't start.

The Battery saver will disconnect any system to prevent discharge below a minimum threshold. Unfortunately, when the Alternator is working extra hard to charge a really bad battery: it will disconnect the charging circuit because it reads the Draw going to the Alternator to produce the power as a parasitic drain. Even at 70mph I have seen the charging disconnected and the vehicle coast to a stop when the electric runs out.

The last system worth mentioning is the Starter interlock. Under the dash and at the top of the Brake pedal lever is a switch. When you press the brake pedal, the switch allows the starter to crank provided the shifter is not in D or R. Drivers feet routinely hit this switch and either move it or break it. When it breaks it can short and drain the battery.

As you mentioned a Random problem, the Brake switch can shake to create a random problem if it is loose or broken. Your rear brake lights can be affected.

With the horn honking, at least part of your problem is the Alarm system. You can have a bad ignition switch too, which reads the keychip to disable the alarm. Your keychip may be bad and setting off the Alarm.

I had a new Lincoln myself which set off the Alarm randomly. I actually slept inside the car one night so I could turn off the alarm in the Apartment complex parking lot. Did'nt know if it would start again if the battery was disconnected and then reconnected. The Battery was shorted with less than 1000 miles on the car. It was a factory defective battery less than 3 months old.

But your car has many years and miles on it so it was worth mentioning the wear items. I hope my solution is helpful.

I couldn't turn off the security alarm on my 1999 Pathfinder as I replaced the battery,
Solution: I read the solution here to disconnect the positive cable, open the driver's door, insert the key, then reconnected the positive cable, while honking, I turn the key to the left, to the right and to the left again while the door is still open. The honking stopped. Then I started the truck without a problem. Thank you for the hint.

My 02 trailblazer pulled that stuff on me. Finally disconnected both battery posts, touched together for 60 seconds. Pulled both PCM fuses together, reinstalled, reconnected the battery and started fine. Gremlins at play I guess.

Try disconnecting the battery and cleaning the terminals/connections,then reconnect the battery and see if the problem persists.

Look Around Engine Compartment For A Loose Or Corroded GROUND, Like Battery To BODY They Are Sensitive to Bad Connections

Try closing all the doors and locking and unlocking the doors with the remote,that should take it out of anti theft mode.

Ah but did it solve the transmission problem?