Alarm going off on some mornings - already replaced hood sensor and IMS
 

Hi All,

Wondering if anyone else has encountered this issue.

About 2 months ago the alarm for my 2013 X5 would start to go off on random mornings. The car is parked outside and it seemed like the alarm went off around the same time around 8:20AM after the sun hits the car (but the alarm didn't go off every morning).

I had the hood latch sensor replaced, but the alarm still went off. I then noticed that if I disabled the Interior Motion Sensor (IMS) by double locking then the alarm wouldn't go off.

I brought the X5 to my indy and their AutoLogic read out that the alarm log was filled with entries saying the IMS was what triggered it. They replaced the IMS (the entire front ceiling dome in the front of the car), but the alarm STILL went off on a couple mornings. If I double locked to disable the IMS then the alarm wouldn't go off in the mornings.

Brought the car back to the shop and again it read as the IMS triggering the alarm. The shop is trying to get the IMS part warrantied for a new replacement, in case somehow the one they installed is bad.


Any ideas? Anyone else experience a similar issue?

We have an issue where if we park the car nose down and out in the driveway, the alarm will go off a few times a day on bright sunny days (ambient air temperature varies and doesn't seem to change behavior). If we park it nose up, which sees less sun, we never have a problem. Ever. Strangely the same behavior is exhibited by our f15 x5. Have done no actual diag but the sun seems to be triggering a sensor somehow.

That’s very interesting…I did flip the X5 direction around so that the tail was facing East, but the alarm still went off right before noon that day (first time ever that the alarm went off any time other than the 8:20-8:30am timeframe).

Oddly for me, this problem only started recently in the past 2 months or so. I’ve had the car since last September and have parked the car in the same spot and same orientation and the alarm didn’t start triggering until recently.

But it does sound like we may be experiencing similar issues where light/temperature may come into play.

You tipped off a clue that is huge and where to look:

Lock twice disables two things:

Internal motion sensor
Vibration/tilt sensor.

I'm betting something is up with the tilt sensor making it too sensitive and setting off the alarm.

Not sure if you can read how tilted etc with a scanner but that's the avenue to explore.

We don't think it's the tilt sensor because the alarm log read out using the AutoLogic only reports the interior motion (ultrasonic) sensor. Even after the shop replaced the IMS and cleared the logs, the new alarm log entries showed the same interior sensor.

See the attached photo of the alarm log readout. This was from before the IMS was swapped out, but the shop told me the alarm log post-IMS replacement shows 5 new entries of the same message.

Check the condition/health of your vehicle battery. Random alarm is one of first symptoms of low system voltage from weak battery. I have had same issues with both e53 and e70. New battery solved issue.

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Alarm going off on some mornings - already replaced hood sensor and IMS
 

The sensor says ultrasonic but may also detect heat signature or something getting heated makes a noise. It's designed to not trip from a slow change but I suspect when it does trip the sun lines up just right to cause the problem.

Why didn't it to before? Because the sun's path changes though the year and didn't line up just right.

I'll bet if you watch how the sun hits your car you can see some magic alignment. You may be able to resolve as simple as a sun shade.

Battery was replaced back in October last year...so it shouldn't be the battery.

I've been trying to monitor the sun's alignment, but odd that it didn't start showing up until 2 months ago when it's been parked in the same spot the same way.

Have been using a sunshade everyday ever since I got the car last year in Sept :(

I tried to monitor the sun and how it hit roof area near where the IMS is, but it looks like the car is actually in the sun for a good amount of time before the alarm triggers (when it triggers, since it doesn't trigger every morning).

I'm wondering if maybe some connection to the IMS is loose and when it gets cold enough, metal contracts so the connection becomes an open. Then when the temperature warms up (i.e. via the sun), the metal will expand and make a connection again and that trips the IMS.

Sun is in a different position every day and takes months to move significantly. The symptoms would align with my suggestion that the seasonal change of sun position is why it came about.

Maybe you can set up a time lapse camera?

I'm thinking a stray beam of sun is hitting the car just right perhaps reflected off a house window or anything that can reflect IR light.

Uneven heating sets up some thermal stress and something binds until it "pops" making enough noise to set off sonic sensor.

Consider the concept of a door getting warmer than the body and eventually the door seal will move with a pop (similar to earthquake at fault lines). My tailgate seal was making a horrible squeak every time I hit a bump until I wiped a little bit of spray lubrication on it. It could be something in the car like a water bottle. Temperature and pressure changes can cause them to crinkle.

I've read the motion sensor can detect a bee or moth so they are very sensitive.

My impression is the sensor is sensing something not a connect/disconnect. I think you'd get a code for the device going offline.

I'm thinking something is heating unevenly and causing something to either bind and release like described above or dimple like an old timey oil can. (like a door panel etc).

Thanks for your suggestions and insight, @andrewwynn . Once I get the car back from the shop (assuming they're able to replace the recently swapped out IMS for a new one, under warranty) I did want to run an experiment of parking the car inside the garage to see if that makes a difference. Perhaps I can setup a time lapse camera as well.

At first I thought it may have been a bug inside the car, but then I would've expected the alarm to go off at random times, not just on random mornings around the same time.

Then the recent time when the alarm triggered right before noon after I flipped the car's orientation 180 degrees really threw me off as that was the first time the alarm went off so "late" compared to its normal ~8:20-8:30am triggering.

I know I can workaround this issue by double locking, but I really want to get this fixed if I can...

Also you do want your alarm to be fully functional. It's tricky when things are intemittent.

You can put some cloth tape over the sensor to soften it's ability to hear and possibly help confirm the sensor is actually reading something.

Here's a thought; before I recently replaced most of my rear suspension I would get creaks and pops out of my suspension after I got out of my car. Lasted over a minute some times. There could be a similar situation where the suspension is binding and popping.

If you can figure out the alarm goes off when sun hits a particular corner of your car you can possibly park in the shade for a while then move into sun and sit inside and listen.

I came across this thread:

https://xoutpost.com/bmw-sav-forums/...off-alarm.html

I wonder if this is it...I do use the BMW sunshade and have been using it since we got the car. I've noticed that the wife sometimes doesn't secure the sunshade as well as I do...could it be that as the car warms up that if the sunshade isn't secured well it moves just ever so slightly to trip the IMS??

I also habitually use the BMW sunshade. But I believe our alarms get set off regardless of whether it is in use or not, though have not tested it. Flipping the X5's around (both E70 and F15) so the front of the truck is not in direct sunlight most of the day has a 100% success rate on both vehicles. :dunno:

Interesting...sounds like it may be worth an experiment to try flipping the cars back to facing the sun and not using the sunshade?

I would most certainly look into the possibility.