[TurbineGuy0]

Hello all,

I’m a proud new owner of a Certified Used 2021 X3 M40i.

One of my first projects for this vehicle is to add a subwoofer for a bit more low end punch. Last evening I prepped all the wiring for the amplifier I’m adding and I began the installation.

The first thing I did, was to remove the ground from the battery. I loosened the single 10mm nut and slid off the wiring from the battery post. I did all this with the rear hatch open.

That’s where things went wrong. The alarm immediately sounded, first fairly normal - then really loud. I connected the ground post immediately and tried pressing buttons on the remote to stop the alarm… no luck. Next, the alarm stopped but the exterior lights were flashing (as if the hazards were on).

I immediately noticed that the key fob was not working - all the doors were locked except for the rear hatch which was open - this makes sense as I was only working in the rear area.

I was finally able to open the vehicle using the myBMW app - from there I got a message in the vehicle that the key fob was not present when trying to start the vehicle. I was able to start it by holding the fob in close proximity to the marking on the steering column.

So now, I’m left with a car that doesn’t lock from the inside buttons or out - I’m having to control lock/unlock functions with the app. The vehicle starts, but the comfort access (keyless) features don’t work and the key fob buttons don’t work on either of the remotes I have.

I’ve tried all sorts of research on the problem and most of the posts are related to the battery in the key fob (I tried changing them). This seems like it’s related to some sort of “feature” that cuts power to individual modules when there’s low power. I’m thinking maybe I triggered something that cause the Comfort Access System to disable itself.

I’m traveling a lot the next few weeks so I can’t get to a dealership anytime soon. Is it worth calling roadside assistance for help? Anyone have any thoughts for how to fix?

Thanks in advance =)

[TurbineGuy0]

Just wanted to give an update.

I did a lot of research and it came down to this thread that helped me the most:
https://g05.bimmerpost.com/forums/sh...0&postcount=15

Disconnecting the battery (after unlocking the car this time) for 5+ minutes worked for me. This time, no alarms. When I reconnected the battery, the key fob and comfort access worked great!

Hoping this helps someone in the future having a similar problem.

[AJ1]

Thanks, I could not find a solution anywhere. Disconnecting the battery solved the issue. Lesson learned: next time I disconnect the battery terminal make sure the car is unlocked. As a safety precaution, I left the driver's side door open.