Alarm Going Off

[Rockit]

My 2002 4.4 alarm's will go off now twice a week for no reason.

I had a 7 Series that did the same thing, it was a common problem that the motion sensor in the headliner would go bad. It cost around $80 and two screws to change.

Has anyone here know the fix?

Or can anyone tell me where the alarm horn is s I can disconnect it.

[Google44]

I think the common problem on these is bonnet switch in top left corner. Disconnect it and see if it goes of.

[Rockit]

Thanks I will check that.

The problem is it goes off randomly when armed and will shut right off when unlocked. It's in my driveway each time and no one is messing with it. These cars have a motion sensor if someone brakes the glass. It went bad on my other 7 series.

[tmv]

Originally Posted by Google44

I think the common problem on these is bonnet switch in top left corner. Disconnect it and see if it goes of.

[Qsilver7]

Ditto the above suggestion...one of the most common false alarm triggers for the e39 & e53 is the hood sensor. Both are located in about the same place (just on opposite sides of the engine bay):

The hood sensor is S19 in the image below...located on the right side of the engine bay (perspective is as if sitting behind the steering wheel)...pull its electrical connector X161 then watch for the next few days if the false triggering of the alarm stops:

Not sure what model year your e38 was...but BMW changed the IMS (interior motion sensor) from the FIS type... to a UIS (Ultrasonic) type...which helped "quell" the false alarm triggers from the IMS.

1996-1999



1999-up

[Rockit]

Thanks "Q"

I will replace it but.... if I just disconnect it I wonder if the alarm will work but just not for the hood.

If I disconnect it should I touch the wires together or leave them apart?

Thank you all for the feedback.....you saved me TONS of time

[Qsilver7]

Originally Posted by Rockit

Thanks "Q"

I will replace it but.... if I just disconnect it I wonder if the alarm will work but just not for the hood.

If I disconnect it should I touch the wires together or leave them apart?

Thank you all for the feedback.....you saved me TONS of time

Just disconnect it first to see if it solves the issue. There's no need to "touch" wires together etc...just make sure that the wiring harness doesn't fall into a place that makes it difficult to reconnect if you decide to replace it. But on the e53, I think the wiring harness is in a pretty safe location back near the firewall...it's the e38's hood sensor's harness that can fall down into the engine bay since it's located along the front ridge of the near the radiator expansion tank.

(e38 7 series hood switch...at front of engine bay)

And no, disconnecting the sensor won't affect the ability to arm the vehicle. DWA will continue to monitor the other sensors around the car. IF a sensor is faulting and still connected, then it can affect the anti-theft alarm siren system (and possibly the remote FZV) central locking (if it's a shared monitor). But if a faulting sensor is disconnected...it is no longer communicating with the system, thus the system ignores it and continues to function.

This same type of issue happens on the e38/e39/e46 sedans with the fuel filler door flap. If the actuator is faulting and is connected...it can stop the car from locking remotely...but if you disconnect it (and make sure the fuse in the trunk isn't blown...you can get the system back up and running...as long as the bad actuator is dissconnected.

[jiigan]

Check your battery as well, I had the same problem on a 2004 4.4, the battery was dying and that set the alarm off. Replaced battery and problem went away.

[Rockit]

Originally Posted by jiigan

Check your battery as well, I had the same problem on a 2004 4.4, the battery was dying and that set the alarm off. Replaced battery and problem went away.

Thanks...Battery is one year old. I replaced it with the factory battery...well different brand but makes them for BMW.