My key stopped disarming the alarm with no warning only a half hour after the last time I armed it. I have two keys and the batteries are new. I also couldn't pop the trunk with the key anymore. I could get in the car with the metal key, but the alarm went off. Someone suggested that I disconnect the battery to reset the alarm, but this brought on a whole new set of problems.

I took the advice and at first I thought it worked because the alarm was no longer on when I re-attached the negative battery terminal.
Within seconds of firing up the ignition, though, I realized that my seat controls no longer work. Neither do the mirrors , the locks, the windows, the rearview controls, the moonroof, the windshield wiper, the rear defrost, the directionals, and probably some other stuff I haven't figured out yet.

I can't re-sync anything because nothing physically functions, now. I've read the DIY in Benzworld.org, but it assumes that only the automatic functions are not in sync.
When I press the window controls, nothing happens... rearview, nothing, seats, nothing, directionals, nothing, wiper, nothing, and so forth.
I have no clue what to do.
Any suggestions?

Someone suggested it might be blown fuses so I checked.
No fuses blown at all. I checked al three boxes.
And I disconnected/reconnected the battery once again. Nothing.
Plus, the BAS light comes on.
It's snow country where I live right now, so the malfunctioning windshield wipers, rear defrost, and directionals make it so I can't drive it anywhere to go check it out.
Besides, I was really hoping to find a DYI solution, anyway, because I've seen so many solutions given out here to seemingly greater problems.
Thank god for BMW's. My X5 will get me through this.

I'm thinking whatever malfunctioned the alarm in the first place is still the culprit here?!:wtf:

The alarm is controlled by the PSE(central locking) pump, located under the rear seat. Start there. Make sure that WATER hasn't entered that system.

IF that looks OK then you need a shop with a scanner that can diagnose the INTERIOR network of computers.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I haven't had a chance to check it yet because I've been working, but I'm curious as too whether this pump controls only the alarm or everything else I've mentioned as well.
I don't know much about this car, unfortunately, but with the cost of labor on these things, I'm trying to do as much as I can myself.