[import36]

my car is a 2008 335i Coupe...with a production date of 2/08.

i started experiencing an issue this past December where i would start the car, and the clock/date would be reset. there was also an error indicating low battery...or battery is being drained while the car is stopped/off. i did a here on the forums and found a couple things...so i checked what was recommended with no results. the problem is intermittent and doesn't happen every time i start the car. it also doesn't have to be extremely cold for this to happen. in any case, i figured i'd wait to start a new thread until after i made a dealer visit.

so i brought my car into the dealer this past week for regular maintenance (brake fluid flush, oil change, etc.), and had them check out the problem. this was there finding:

straight from the printout:
"No fix available yet. Perform short test and found nothing in the codes for energy diag or power supply. Perform energy diag anyways. Found that it had turned off the 30gf relay. Perform test plan and it advised that BMW is working on a fix, currently there is none. Diag code D1621_00ENGDIAG_70_902"

my SA told me it appears to be a software programming issue. the DME receives a signal indicating that the battery is being drained, so it cuts power to the clock. when in actuality there is no drain on the battery at all. it's like a false alarm.

has anyone else experienced this?

[m_thompson]

My wife's '08 328xi had the same symptoms. The dealer replaced the battery but the symptoms were back the next day. On the second visit they replaced the negative battery cable which includes the current sensor. Apparently there was't an electrical drain problem. The sensor was indicating a high current flow when there really wasn't much draw on the battery.

[RR335]

It is one of your cables linked to your battery. Have you gotten into an accident with that car? It might be the BST cable.