[immortality]

Hi
I've owned 2012 z4 35is since 2015.
I got few codes from last month. I am not sure the codes are originated from battery issue or actual problems. Here are my questions and Z4 history for understanding issue.

Question #1 – should I visit dealer for OEM battery and balancing stuff if codes come up again?
Question #2 - If code 2A15 is actual problem, does Z4 have a dedicated pressure sensor for gas cap loose? It comes after gas cap tighten warning, so if there is a sensor, I should replace it first otherwise find actual leak from canister closing valve to purge valve which is difficult. ( in addition, I replaced fuel cap last year September 20th, no issues so far)
Question #3 – Am I missing anything that I must check up?

here is z4 history in short.
2019 September - changed after market battery from advanced auto (same spec, no issue until 2020 September)
2020 August to September - i did not turn engine on for 6 weeks.
After 6 weeks, I turned on engine and battery was too low so, I had to do jump up start.
Since then battery does not hold charging for long (cannot last 2days)
Codes started popping up and I keep erasing with code reader device.( I thought it’s from low battery)
2020 September – Advanced auto check the battery and result was OK, and they put the battery on their own slow charger for 24 hours. ( during this time. Z4 did not have any power supply). The battery still cannot last long few days.
2020 October - I went to different store and their battery check device was not able to check so I got battery warranty and RECEIVED new one. I did replace new one by myself.
(I heard they are not supposed to change imported car battery such as BMW due to battery balancing programing. This is what they told me, but i got changed it last year from other store, other technician somehow).
These are the codes popping up now.
- 2A15 DMTL, Minor leak ( before this code, gas cap tighten warning pops up few times)
- 2B28 Throttle valves, test of return springs, bank 2
- 6030 versorgungsspannung - unterspannung erkannt(german - supply voltage - undervoltage detected)