Have no key and alarm keeps going off

disconnect the battery...wait 30 mins and the pcm should reset.

Try disconnecting the neg. battery terminal. Open the drivers door and leave it unlocked then reconnect the battery back up.

what make and model?

Is it factory alarm or aftermarket??. Try using the key to lock and unlock the doors driver and passenger then turn the ingnition on with the key and leave it in the key on engine off position for a few minutes and start the vehicle

I would take it back to the place where the alarm was installed or a dealer that installs that brand of alarm for proper diagnosis.

conect back the battery close all doors and windows driver door insert the key unlock the door one time and hold the key until window goes all way down then turn key to lock the door hold to lock position until windows go up if no stop repeat one more time right way without taking the key out , hope this help.

Try unlocking from the passenger door. Some of these had a key cylinder switch on the back of the lock cylinder which deactivates the alarm. If it works ok from passenger side then the switch inside driver door would need replaced

The fuse for the alarm is under the hood. Give a good look and you should find it. Once you have pulled it it will deactivate the alarm I am not sure if this is exactly your problem since you said that the car wont start.... but it is worth a try.

The ignition security on/off is located at the trunk lock. unlock and lock rear gate and the alarm will turn off. My jeep sat in my drive for a month before a jeep tech told me this. It still triggers the security sometimes when I unlock the passenger door with the key and I go straight to the rear gate lock and it shuts off instantly.