2001 fxdx with the oem alarm.
when I arm the alarm I get the 2 chirps and flashes to signal that the system is armed, but shortly after that the lights alternately flash 3 times and I get a single loud chirp from the siren. This continues with a few seconds in between chirps/flashes and does not stop. Can't figure out how to make it stop! I changed the sensitivity settings but that didn't change anything. I searched but didn't find a way to fix it. Anyone had this problem?

 

Could not running the front turn signals be causing this?

 

battery in the key fob going dead?

have you tried putting in your PIN (i don't know if your year has a pin or not?)

 

Doesn't seem like symptoms of the battery going dead, but that's probably what I'll be trying first. Didn't try the pin as the alarm isn't actually going off. Its one loud beep with some flashing, but it keeps doing it every few seconds. It does it when arming with the fob or when you set it to automatically arm.

 

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It almost sounds like the accelerometer that detects when the bike is upright is not getting the all clear from the security system, my bike does that when I stand it up without the fob close enough, but then it actually starts the siren after a while. Yours sounds as it is almost stuck in the "warning " stage and it keeps looping. Have you tried disconnecting/reconnecting the battery, or removeing the ecm, and reseating it in its connection?
I dunno man I'm just spitballing here
GL