Is there any way of testing my TCU to see if its the cause of my battery drain? Ive already replaced my IBS cable with the revised version, new battery, new alternator and im still getting a battery drain from somewhere. Let me know what you guys think because im really determined to find this electrical gremlin. Tired of disconnection my negative cable every time the cars not in use!

 

You can test with amp clamp

 

im not even entirely sure what id be looking for. Can i temporarily disconnect the TCU for a few days to see if my battery will continue to drain?

 

yes

 

I have been fighting this battery drain for serveral months now and I have finally resolved it... Early august my battery went bad so i went to a local garage and had a new battery installed... Not really having much of a clue thinking batterys are all the same as long long as the shape is same and fits in the slot... So from then on every time i left the car for longer than ten minutes my battery would be drained to a point of non start... So this resulted me in taking my negative power cables off every time i left the car.... After visiting half a dozen garages and going bald in the process... I came across a post were it mentioned if the same amp battery was not installed it can cause a battery drain... So i rang up dealers and was told i needed a 110 amp battery, so went out and purchased a bosch s5 110 amp battery... Its been a week now and i dont have to disconnect my power cables anymore and every time i go to start car it does not feel like it is under powered and will just about to turn over engine to start car.... Im so relieved as this was actually getting to me... I tried using the amp meter pulling out fuses one by one and nothing worked as these cars take 20 mins to go to sleep.... Hope this helps someone else in resolving their problems with battery drain issues as it has resolved mine....

 

You are supposed to register the battery to the car. If your old battery was different type & rating I can see that leading to battery issues.

SW Bimmers can do it for you buddy.

The bmwhat app supposedly can do it w/ an in app purchase but I haven't bought it b/c my battery is good.