I have a 2001 Nissan Altima GLE and the factory installed security
alarm goes off for no reason and with no warning. The horn may start
blowing while going down the road, sometimes in the middle of the
night, or when a person approaches the car.

I disconnected the Security system relay but that did not silence the
alarm. I disconnected the security system fuse, the security system
light on the dash goes out but that does not silence the alarm. I did
replace the batteris in the FOBS thinking that perhaps a low battery is
casuing the problem. The only way I am a ble to silence the thing is to
disconnect the horn.

Has anybody run into this?