[h20man04]

I am a new owner and the car is dead after sitting in my garage for a week (not ideal). I am not quite sure where the battery is located for the wagon and all googling points me to the non-wagon.

[Billfitz]

It's under the trunk floor, behind the right rear wheel well.

But first things first, charge it using the under hood charging posts. Whatever you don't replace it until and unless you've confirmed it's bad. Parasitic power drain is a common problem.

[h20man04]

Thank you. and how would I diagnose this power drainage?

[cleaver]

h20man, bear in mind that if you have a 2012 328 wagon, that's an E91. The battery may be in the same place (PITA to get access), but this board references the F31 (2014 - 2019).

[Billfitz]

Originally Posted by h20man04

Thank you. and how would I diagnose this power drainage?

https://www.autozone.com/diy/battery...ur-car-battery

[Orion4]

Once you fully charge the battery (if it takes the charge), have Batteries Plus or an auto parts store performa load test. That will give you a more complete picture of the health of the battery. If this is still the original battery, probably a good time to replace it.

I had Parasitic discharge on my 13 F30 335i and turned out to be the electronic module on top of the electric water pump. It was not going to "sleep".