Electrical problem?
 

Has anyone experienced this or may know what is causing this?

The other day my '02 X5 4.4 was dead so I jumped the battery, drove it for 20+ minutes, and parked it. Later that night my factory alarm went off, I went out to turn the alarm off, and everything seemed dead....door locks, etc. Then, the alarm starting going off (battery must be OK) & I could not turn it off.

My battery is about 3 yr.s old now and I replaced the alternator about 3 yrs ago also.

This sounds electrical, any ideas?

Thank You

Almost exactly what happened to mine (2004 4.8is). Although I got 5 days between mine refusing to start again. Since then, had it at my mechanics for 3 days but he couldn't find anything. Was going to take it to BMW service for some diagnostics but hasn't happened again (past three weeks). My bro is a sparky and we cleaned every main connection we could find to ensure good contact was being made. This was about 1 week after last failure to start so can't say it fixed the problem but may have helped.

Good luck with the diagnosis

First, the alarm siren has it's own rechargeable battery...so it will work (for a while) even if the vehicles battery is dead. It will eventually die if it is not being recharged by the vehicles battery.

Second, have you unlocked your instrument cluster so that you can perform OBC TEST #9 (which will reveal the battery's voltage with the engine NOT running and ignition in position 1)? Or do you have a multi-meter so that you can check your battery's voltage to make sure that its voltage isn't dropping low? A battery voltage of 11.89 volts means that the battery is at 0% state of charge. Which means that there could be some reserve capacity in the battery to operate some light-weight electronics.

Low vehicle battery voltage will also cause the DWA's alarm siren to sound off...when the central locking system is activated when the car's battery voltage is low...the DWA alarm can interpret this as a thief trying to disconnect battery power...thus it sounds off.

Double check the health of your vehicle's battery with some type of testing equipment that will provide voltage numbers so that you can truly dismiss it as the culprit.

And if your instrument cluster is displaying the BATTERY charge warning light...that would indicate that the alternator is not keeping the battery charged...so take another look at the alternator if this is the case.

Good luck.

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Not sure about your battery problems, but the alarm sounding at random could be a faulty hood switch, which I have personally experienced in 2 different E53's.

Unplugging the aforementioned hood pinswitches stopped the random alarm tripping. Have not gotten around to replacing the switches, but I read a lot of other people just leave it unplugged.

from your symptoms - take the battery to an autoparts store, have them test it for dead cells... usually it is free... get a new battery, about $90 with 3 year warranty... this will eliminate some of the concerns, then you can move further in troubleshooting...

alarm is triggered when the battery is about to die, it also triggers engine kill switch.. when new battery installed, you cycle alarm with key, and then you can start the engine... last ditch effort to prevent theft...