I recently purchased a 2004 545i CPO and after about a week, the alarm started to go off when I would turn the key in the ignition. I took it back and had it worked on for about week. They said it was something to do with the motion sensor? It worked perfectly for 2 weeks and now about every other time I get in the car and turn the key, the horn starts honking and the headlights blinking. It will let me start the car and drive it, but the horn keeps blaring. It usually takes me 4 or 5 attempts at trying to start the car before it will start normally.

Does anyone have any idea what is wrong? Has anyone ever heard of this? I don't think that my dealer has any idea what is wrong.

Thanks.

well, take it back and tell them to fix it.

I have an appointment to take it in, but I was just curious if anyone had ever heard of such a problem.

I had an e60 with a horn that blared periodically, but the lights were not affected. Turned out to be a shorted horn circuit.

Thanks bmwQ.

I think that you may be on to something. The horn has started to blare off and on while I drive it. I was probably mistaken about the lights b/c I usually leave for work while it is dark and park in a dark parking deck, so they are just coming on automatically.

I set off the alarm myself and that siren is definitely different than what I am hearing.

I have an appt. to have it worked on in 2 weeks, but I think I may just take it over there today and leave it because it is driving me insane. I'm worried I am going to get shot for honking at someone at a stop light or while driving down the road.

Haha!! I'll bet that's what it is then. My service writer wrote the complaint up as "customer states alarm goes off randomly, please check and advise". I drove the heck out of the car and nothing happened. At the end of the day I went out to drive it one last time and as soon as I turned the key to the on position, the horn blared non-stop. I questioned the service writer about it ("I can't duplicate the alarm complaint, but the horn has issues...") he came back with "horn/alarm, same thing, right?". Wrong. In my case, a complete new driver airbag unit was required (the horn circuit is integrated into the airbag unit). Good luck. It sure sounds like the issue I saw.
Let me know how it turns out!
Q

I left it at the dealership last night. I'll let you know how it goes.

You were right again! They just called and said they had to replace the driver airbag because it had a bad contact.

Sweet!! Glad to hear it worked out.

BMW0 is so bright that his parents nicknamed him Sunny.

BMW0 is so bright that his parents nicknamed him Sunny.

lol...my bulb just flickers periodically. You'd stump your toe in the darkness of my head.