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I recently picked up a CPO '21 GLE 450 equipped with the 852 - Advanced Alarm System option. I've noticed that the tow away sensor and interior motion sensors are very inconsistent. They'll be on for a day or two and then I'll be unable to activate those sensors via the MBUX screen. Tapping on the buttons, they'll appear to activate but then turn off again after about 2-3 seconds. I was at my selling dealership today for something unrelated, but decided to ask my service advisor about it. He told me that the tow away sensor should only be activated when the vehicle needs to be towed (obviously not the case) and that the interior motion sensor was linked to the MBUX WiFi subscription (again, not the case). Although, I did see something about tow away and collision detection being one of the 'Digital Extra's' through MercedesMe, but we do subscribe to that service.
Has anyone determined an actual fix for this issue? I did find threads on this topic, but they were 2+ years old and I was unable to reply.
Last edited by AndyT3; Mar 6, 2025 at 06:58 PM.
Reason: Added photo
I wouldn't trust that advisor. Our tow alarm and interior alarm are active by default and we have no Mercedes me sub. I have to remember to turn off the interior motion sensor if the kids stay in the car during a quick stop or the alarm will trigger.
It's my understanding that they function as you described - on by default and only disabled if you deactivate them through the MBUX screen for a situation as you've described.
I sent an email to the service manager to see if there are any bulletins or techs that have worked through a similar issue, as well as to try to get it in for diagnosis. He has yet to reply, but hopefully I hear back on Monday.
Edit to add: We do have an air freshener hanging from the rearview mirror. I assume it's possible that it detects that motion and therefore automatically disables the sensor? But then again, it'll randomly activate and deactivate those two sensors so who knows.
Last edited by AndyT3; Mar 7, 2025 at 04:00 PM.
Reason: Additional information
It's my understanding that they function as you described - on by default and only disabled if you deactivate them through the MBUX screen for a situation as you've described.
I sent an email to the service manager to see if there are any bulletins or techs that have worked through a similar issue, as well as to try to get it in for diagnosis. He has yet to reply, but hopefully I hear back on Monday.
Edit to add: We do have an air freshener hanging from the rearview mirror. I assume it's possible that it detects that motion and therefore automatically disables the sensor? But then again, it'll randomly activate and deactivate those two sensors so who knows.
2/21 the vehicle was parked in the parking lot at work. It must have picked up dust or something in the vehicle. It was disabled from that point on for about a week. It then allowed me to activate both the tow/collision sensor and motion sensors, and they remained on every time we locked the vehicle for about 3-4 days. After that point, I noticed they were showing 'Not Active' in the app, and I couldn't activate them via the MBUX screen in the vehicle. It seems pretty random when they actually allow you to activate them and when they turn off and don't allow you to turn them back on.
Hopefully I'll have an update this afternoon - we dropped off the vehicle and service is taking a look at it today. Our GLS loaner has the advanced alarm system and you can enable/disable the tow/impact sensor and interior motion sensors normally. We'll see...
Just received an email from my service advisor - Completed a software update on the overhead control unit. From what I can see in the MercedesMe app, the tow and interior motion sensors are working... for now anyway. We'll keep an eye on it and hopefully this will be the end of it!
Last edited by AndyT3; Mar 12, 2025 at 02:37 PM.
Reason: Adding information
Hopefully I'll have an update this afternoon - we dropped off the vehicle and service is taking a look at it today. Our GLS loaner has the advanced alarm system and you can enable/disable the tow/impact sensor and interior motion sensors normally. We'll see...
Just received an email from my service advisor - Completed a software update on the overhead control unit. From what I can see in the MercedesMe app, the tow and interior motion sensors are working... for now anyway. We'll keep an eye on it and hopefully this will be the end of it!
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Tow Away and Interior Motion sensor issue
