My head lights were flashing and car would not start. I disconnected battery hoping to reset problem. After playing with alarm silence(horn button on keylock) got lights to stop. I got the truck started, but it would not shut off. I had the key out of the vehicle and it was still running. Had to pull the ignition fuse and disconnect the battery. Is it my ignition switch?

1. Unlock the car manually. If the alarm remote is not working, use the key directly. Often times opening up the door will stop the alarm. If the driver's side door won't unlock, try the passenger door.

2
Turn on your car. Put the key in the ignition, and turn the car on. If this doesn't turn off the alarm, try turning on and off the dashboard lights a few times without revving up the engine.
3
Utilize common tricks. Factory car alarms have some simple reset protocols to help turn off an alarm. Most of the tricks rely on using the key in the door; simply put, a lot of factory car alarms have a door sensor, so working with the door might be the go-to for a quick fix.
Put the key in the driver's door and turn it twice to the right, then twice to the left. Then insert your key into the ignition and start the car.
Turn the key into the unlock position and hold it for two seconds before opening the door.

4
Disconnect the battery. If the alarm is still sounding after the initial troubleshooting, you'll want to silence the siren as quickly as possible. Car alarms rely on the electronic component of the vehicle, and disconnecting the battery should both silence the siren and reset your alarm. Open up the hood, locate the battery, and with a wrench, remove the negative terminal. Then reconnect it after a minute has passed.
If it is more easily accessible you can also unplug the wiring harness that connects to the car's horn or siren. If the horn or siren gets unplugged it can no longer make noise.

5
Reset the alarm unit. Locate the alarm and transmitter system; refer to your owner's manual for the exact location. Hit the reset switch or turn it off and on.

6
Remove the alarm fuse. This should both silence and take the alarm out of commission until the fuse is replaced. Find the alarm fuse in the fuse box. Remove it, and put the fuse in a plastic bag. You can store it in your glove compartment for safe keeping.
If you cannot locate the alarm fuse right away, remove fuses to see if the alarm will stop. Doing this will not cause damage to the car, but make sure you return the fuses after you've determined they are not for the alarm.
Some car alarms, when tampered with, prevent a car from starting as an anti-theft function. If you remove the fuse and cannot start the vehicle, you will have to take the car to a mechanic or dealer.

7
Press the "panic" or buttons on your keychain remote to stop the alarm. Because the "panic" button can sound the car alarm, it can also stop it. Pressing "unlock" or the "trunk" button can stop the car alarm because it disarms the car's security system.

8
Seek a mechanic if problems persist. If none these reset methods work, try speaking with a mechanic or dealer. If they can recognize the issues over the phone, the fix might be simple. However, further diagnosis might be needed in person.

https://www.wikihow.com/Disconnect-a-Car-Battery

DID YOU PRESS YOUR ALARM REMOTE TO DISARM THE SYSTEM OR DOES THE CAR START IF NOT DISCONNECT THE CABLES AGAIN AND THEN RECONNECT WHEN THE ALARM STARTS (YOU MAY NOT HAVE A HORN)FLASHING LIGHTS PRESS THE DISARM BUTTON ON THE REMOTE AFTER THAT SET YOUR CLOCK IF THIS DID NOT HELP BEING MORE SPECIFIC WILL I'M NOT THERE WITH YOU

lock vehicle with either remote or use lock button on door inside car...then goto passenger side door and unlock it with key..this should reset it

Inserting the key in the ignition and turning it on can work sometimes, but do you not have a remote for the alarm? Check the battery in the actual remote if you do have one. the alarm sounds as if (by your description) it has a back up battery, if so, youll have to locate IT and disconnect it, and that should reset the alarm. Without details, its shots in the dark here. Learn your vehicle, and contact a dealer to speak with someone who Should know his product. If your attempting to steal the vehicle as we speak, then I suggest you just run. ;O)

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.

take out the alarm fuse! :D

If a aftermarket alarm then disconnect it ,these auto remote start alarm things are useless and all go wrong with age

That is the security system coming on.

try disconnecting the battery neg lead and the pos lead then join them together for 5 mins then reconnect the battery and see what happens ,it might just reset the fault for you .

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.