Stock Alarm goes off when unlocking car

[Toxarch]

This just started recently and I have no clue why, thought maybe someone here knows anything about it. When I unlock the car with the remote on the key, the alarm goes off for 30 seconds and then quits. Doors and truck are closed and unlocked after pressing the button. I can turn the key in the door and that doesn't stop it. I can even put the key in the ignition and start the car while the alarm is going off. It happened once the other day and then was fine after. Then it happened twice today.

Any ideas? Maybe a door sensor is messed up or something? I tried pressing lock twice to turn the alarm shock sensor off but that didn't do anything. The alarm siren sounds as soon as the unlock button is pressed.

[Edwin NL]

That is weird!

Have the alarm recoded, could be a setting that got messed up

[Toxarch]

I thought maybe the unlock button was getting stuck and activating a panic alarm, but the alarm sounds as soon as the button is pressed.

The alarm used to "chirp" when locking and unlocking. Doesn't do that anymore. Maybe that has something to do with it?

Who can recode the alarm? Do I have to go to the dealer to do it?

[Edwin NL]

Panic function is when you hold the trunk button.

You could try to pull the battery overnight see if that solves something

[Sabreslight]

I also had this happen the other night, my car has been parked for a few weeks so i go over last night to test something out and when i use my remote to unlock my alarm goes off, but i didn't wait long enough to see if it would go off by itself.

[Millenium750ia]

It happend to me when one of the tvo batterys were bad. Replaced it with new one and it havnt had any isues since.

[Sabreslight]

It happend to me when one of the tvo batterys were bad. Replaced it with new one and it havnt had any isues since.

Does that still apply to the 740's since they don't have dual batteries?

[sumadaz]

My 98 740i just did this today. I go out to unlock the car and the alarm sounds. I jump in and try to start it up and it clicks once but doesn't fire. I got the alarm shut off and try to start again and nothing. All the lights on the dash are dim. Bad battery? Anybody have an idea on what a new one costs?

[TheJayP]

My 98 740i just did this today. I go out to unlock the car and the alarm sounds. I jump in and try to start it up and it clicks once but doesn't fire. I got the alarm shut off and try to start again and nothing. All the lights on the dash are dim. Bad battery? Anybody have an idea on what a new one costs?

Check e38.org, there are a couple battery options that are a LOT cheaper then OEM BMW. I personally have the duralast suggested on e38 and It works like a charm.

[Qsilver7]

...my car has been parked for a few weeks so i go over last night to test something out and when i use my remote to unlock my alarm goes off, but i didn't wait long enough to see if it would go off by itself.

The situation you describes sounds like a classic battery issue (its discharged from sitting for a long period of time). When the battery voltage drops real low...it can no longer keep the alarm siren's (internal) battery charged up. So when a request is made of the system, the alarm sounds off due to the drop in voltage...which signifies to the alarm siren that someone is trying to steal the car by disconnecting the battery...or something or other.

Check the health of your car's battery...if you do TEST 9 BEFORE starting the car (which puts a surface charge on the battery)...you should see voltage above 11.89v. If you don't know how to do TEST 9...just do a search...Edwin has even posted a video (on YouTube) on how to access TEST 9. If searching on youtube (instead of here) look for videos by "Homerraas" on how to UNLOCK the OBC etc.

My 98 740i ...I jump in and try to start it up and it clicks once but doesn't fire. I got the alarm shut off and try to start again and nothing. All the lights on the dash are dim. Bad battery? Anybody have an idea on what a new one costs?

Yep...your car's battery is probably toast. Again, TEST 9 can quickly determine if the voltage is lower than normal.

Do a search on the forum or google using Duralast 49 DL and you should find many past threads discussing replacement batteries. Some brand names oft discussed are:

• Duralast 49 DL or 95R Gold (sold @ AutoZone) approx $99
• Interstate MTP-93 or H8 or H9 (www.interstatebatteries.com for local reseller)
• Rayovac H9 (sold at Batteries Plus)
• AutoCraft 49-1 (sold @ Advance Auto)
• DieHard Interstate 49 or 95 class size (sold @ Sears)
• EverStart 48 or 49 (sold @ WalMart)

[Sabreslight]

The situation you describes sounds like a classic battery issue (its discharged from sitting for a long period of time). When the battery voltage drops real low...it can no longer keep the alarm siren's (internal) battery charged up. So when a request is made of the system, the alarm sounds off due to the drop in voltage...which signifies to the alarm siren that someone is trying to steal the car by disconnecting the battery...or something or other.

Check the health of your car's battery...if you do TEST 9 BEFORE starting the car (which puts a surface charge on the battery)...you should see voltage above 11.89v. If you don't know how to do TEST 9...just do a search...Edwin has even posted a video (on YouTube) on how to access TEST 9. If searching on youtube (instead of here) look for videos by "Homerraas" on how to UNLOCK the OBC etc.


Yep...your car's battery is probably toast. Again, TEST 9 can quickly determine if the voltage is lower than normal.


Do a search on the forum or google using Duralast 49 DL and you should find many past threads discussing replacement batteries. Some brand names oft discussed are:

• Duralast 49 DL or 95R Gold (sold @ AutoZone) approx $99
• Interstate MTP-93 or H8 or H9 (www.interstatebatteries.com for local reseller)
• Rayovac H9 (sold at Batteries Plus)
• AutoCraft 49-1 (sold @ Advance Auto)
• DieHard Interstate 49 or 95 class size (sold @ Sears)
• EverStart 48 or 49 (sold @ WalMart)

Thanks for the heads up.

[523i]

Hi

I`ve found your forum exploring net for my problem and i can say that this is really good place for all BMW lovers.

I have the same problem. My alarm starts to beep when i unlock the car and not immediately but 1-2 seconds after i unlock it. I`ve checked my doors and all are closed. Using OBC test #9 voltage is 12.6 when the engine is off. I`ve also tried to disconect my hood sensor because i`ve found it as a common problem. Also i have turned off motion/tilt sensors and the problem is still there.

So any new solution? Thx!

[black740ia]

i also was going to suggest the hood sensor....

[Qsilver7]

Hi

I`ve found your forum exploring net for my problem and i can say that this is really good place for all BMW lovers.

I have the same problem. My alarm starts to beep when i unlock the car and not immediately but 1-2 seconds after i unlock it. I`ve checked my doors and all are closed. Using OBC test #9 voltage is 12.6 when the engine is off. I`ve also tried to disconect my hood sensor because i`ve found it as a common problem. Also i have turned off motion/tilt sensors and the problem is still there.

So any new solution? Thx!

Welcome to the forum.

The one thing you didn't mention checking is the alarm siren itself. The alarm siren could also be the problem if its internal battery is no longer keeping a charge.

As mentioned on my post above...the car's battery should keep the alarm siren's internal battery charged. And your car battery seems to be okay at 12.6 volts. So that could possibly point to the alarm siren's battery beginning to fail.

What is your car's model year (or build date)? That would help us in determining the age of some of the components in your car...or what systems where used at the time of its production.

The alarm siren is located in the rear right wheel well...behind the wheel liner. Just for an understanding of where the alarm siren is located (and what it looks like)...you can see pics & instructions at this DIY write-up from BMWtips.com: http://www.bmwtips.com/tipsntricks/t...eplacement.htm

The alarm siren is #6 in the diagram (below) and part nbr index at this link: http://bmwfans.info/parts/catalog/E3.../alarm_system/

[523i]

@Qsilver7
At first thank you man!

Well, my car is E39 523i and was built in April 1997.

It seems that now only alarm siren can cause this problem and i will check it. Can you tell me if the internal battery of the siren is broken can i change only that battery or to buy new siren? Than do you have some advice to check siren before buying new one?

[Qsilver7]

@Qsilver7
At first thank you man!

Well, my car is E39 523i and was built in April 1997.

It seems that now only alarm siren can cause this problem and i will check it. Can you tell me if the internal battery of the siren is broken can i change only that battery or to buy new siren? Than do you have some advice to check siren before buying new one?

The internal battery for the most part is not meant to be replaceable (just like the newer style keys). But anything can be done with time, money, resourcefulness, access to parts, etc. By the time most can source a replacement battery and open up the siren to replace etc...buying one or finding a used one would be easier.

As far as testing...there's always the BMW dealership which can hook up their diagnostic GT-1, MoDiC, or DIS equipment and communicate with the DWA system (anti-theft alarm system) and see what has been causing the false triggering. If you have another BMW owner/friend...you all could swap your alarm sirens...I believe the e46/e31/e38/e39/e52 (Z8)/e53 (X5)/e83 (X3) all use the same alarm siren. (BTW, there are approx 3 different sounding sirens depending on build date...the early ones back to 95...then the wolf whistle between 96-98...and then the road runner "beep beep" from 99-up) And if your good with electronics...you may have equipment that can test the capacity of the alarm siren's battery.

I feel your pain...because it could be a waste of money just buying parts...not knowing if it will solve the issue. So if you know anyone that has diagnostic equipment that can communicate with the BMW proprietary systems...then at least you'd get an idea of where the culprit is hiding.

Good luck.

[523i]

I have to say one more thing

A few minutes ago i`ve disconnected again hood sensor to check again, but the problem was still there. After that i decided to disconnect my main battery for a 30min to reset system. Is that clever or not i don`t know Well we are going to see.

But what i wanted to say is that the car was unlocked when i unpluged - from battery and in that moment siren turns on for a maybe 2seconds. For me it is also strange and it seems to me that internal battery is in really bad condition because it sounds only 2s. What do you think, am i right?
But again why does the siren turns on when the car was unlocked?

Ok man. Thx for that post! I will try with diagnostic and of course i will post what the real problem was. I am going to holiday soon without the car so maybe i will not solve that but after that i will have to because i will go to 2000km trip in a few days.

[Qsilver7]

... i decided to disconnect my main battery for a 30min to reset system. ...the car was unlocked when i unpluged - from battery and in that moment siren turns on for a maybe 2seconds...

That little scenario (unplugging car battery & alarm siren goes off)...again would make me look real close at the alarm siren's battery being the culprit. It's only a "theory" at this point since we haven't communicated with the DWA system to find the fault codes left...but the siren really looks suspect.

Good luck & have fun on holiday.

[523i]

Good luck & have fun on holiday.

Thx.

Now i`ve connected the battery and turned on the engine for a few minutes. And after that it is all normal, without anoying sound
I have tried to lock/unlock several times and everything is ok. Maybe it helped

I will see if it help and post the real solution

[523i]

Reseting sistem didn`t make effect. Isn`t fixed yet.

Yesterday i`ve removed my siren using tips from here. And i can say it was very helpful. Today i wanted to check it on some places, but they didn`t know, because they don`t have proper diagonstic tools. Tomorow i am going to another place to check it. After that i hope, that finally i will be sure what the problem is. I can check it in some dealerships but it would cost me like new siren... That will be my last decision

[MrEnizzle]

i also was going to suggest the hood sensor....

I had a Q45 that the hood sensor was jacked up.. took me running out of my house 4 times in my drawers and my pistol before i figured out what it was..

[523i]

I`ve arrived yesterday and my car is fixed
I was on holiday and in meanwhile my father has driven the car to one electrician and he is some kind of freak for BMW and fixed it for about 30$.
Thx to all for help!

[AugustBMW]

Hi, what was the problem???

I`ve arrived yesterday and my car is fixed
I was on holiday and in meanwhile my father has driven the car to one electrician and he is some kind of freak for BMW and fixed it for about 30$.
Thx to all for help!

[Padden]

And what was the problem!???

Damn I hate when people leave thread without telling what was the problem. I'm dealing with exact same problem..

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