BMW X5 new battery andtick over

Someone else with same problem ,might help ,



I Have to share my absolute joy, at last the thing that has spoiled a pretty good car has a last been solved.

I've been plagued by flat battery's for nearly three years, BMW had the car to look at when the problem first arose and straight away diagnosed a heater fan final resister as the culprit.
well this stopped the fan speed rising and falling at will but the battery would still go flat if not driven for 24 hours.
This meant carrying a power pack in the back just incase of the embarrassing failure.
The last weekend found the battery going flat overnight, so enough is enough back to BMW with it.

They have always said they could't find a problem, and this week for the first day of looking they could not find a drain' so they left it over night with an oscillascope attached and hey presto!! the thing came to life in the middle of the night, they recorded a 2 amp drain. Next day they left it asleep or so they thought in the corner of the workshop.
The mechanic wandered over to check if anything had been going on just at the right time, as he looked the thing flickered into life, so while it was active he started pulling the different module fuses out and when he pulled the telephone command module fuse it stopped drawing.At last problem sorted, as i don't use the phone in the car it won't be a problem not to have it anymore.Just glad to have found the problem, I hope this helps someone out there who is having the same problem.

A Very Happy Bizzy


VxDuncan

2,278 posts

66 months
[report] [news] Friday 13th November 2009
Have you not just cured the symptom, not the cause though? The vehicle has been woken from sleep mode, allowing the telephone module to power up a draw current. Obviously, you've reduced the draw buy removing the phone. However, I seriously doubt the phone module is able to send a message to wake the vehicle from sleep mode (unless there is a safety critical reason why it would be able to - possible for tracking purposes?), so something else is likely to be waking it from sleep. All the time it is awake it's drawing more current than it should - it's quite possible the other modules (esp the body controller and major CAN gateways) will flatten the battery after a couple of weeks. I wouldn't want to be leaving it in an airport carpark while you go away for a couple of weeks as is.

Worth trying to find what the cause is - now if you had access to the BMW CAN spec you could monitor the bus and look for certain message ID's to figure which module was waking it out of sleep, but I guess only BMW could do that. There might be previous of this in BMWs records?