Did you get the dreaded "Auxiliary Battery Malfunction" alert in your vehicles instrument cluster screen? In this DIY how to video, we'll show you how to locate your Mercedes auxiliary battery and how to replace your auxiliary battery for your 2011 Mercedes Benz E350 after you get the auxiliary battery malfunction Mercedes Benz alert.

Mercedes auxiliary battery malfunction E350 (W212)

Our advice here should work for most cars that have an auxiliary batter installed, and should still be a good guide for your auxiliary battery replacement. It's all a matter of knowing where your auxiliary battery is installed in your car. In the case of this 2011 Mercedes E350 (W212), we show you the Mercedes auxiliary battery location.

✅ MERCEDEZ BENZ AUXILLARY BATTERY: https://www.amazon.com/2007-2012-Mercedes-Benz-Auxillary-Battery-000000004039/dp/B06Y2NDM2F/ref=sr_1_5?keywords=mercedes+auxiliary+battery&qid=1692668791&sr=8-5&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc
✅ TORX SCREWDRIVER SET:
https://www.amazon.com/Magnetic-Screwdriver-Screwdrivers-Gloss-Steel/dp/B0BVQFW2TP/ref=sr_1_2_sspa?keywords=Torx+T20+screwdriver&qid=1692668889&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1
✅ 10 MM SOCKET:
https://www.amazon.com/Crescent-CDS17N-Drive-10mm-Socket/dp/B078Z3978H/ref=sr_1_5?crid=1U74MA6MBHPQB&keywords=10+MM+SOCKET&qid=1692668931&sprefix=10+mm+socket%2Caps%2C90&sr=8-5
✅ PLASTIC PRY TOOL:
https://www.amazon.com/GOOACC-Removal-No-Scratch-Dashboard-Dismantle/dp/B0B6W1MRB2/ref=sr_1_1_sspa?keywords=plastic+pry+tool&qid=1692668961&sprefix=PLASTIC+PRY%2Caps%2C94&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

Auxiliary battery function Mercedes

It does not matter if you have an auxiliary battery malfunction S550, or an auxiliary battery malfunction E350, it is essentially the same failure mode of your Mercedes auxiliary battery. The purpose of the auxiliary battery is to backup certain systems of your car, and in the case of the Mercedes Benz w212, and other Mercedes models with auxiliary batteries, they supply power to the ECO mode system, which allows your gas motor to shut off while your foot is on the brake during traffic lights. Your Mercedes-Benz w212 auxiliary battery also provides power for the hold function on your brakes.

Auxiliary battery replacement Mercedes W212 models and more

For some Mercedes owners, just finding where the auxiliary battery is located in their model is half the battle, and some have full sized motorcycle type batteries, while other Mercedes models have auxiliary batteries the size of a chuck of fudge. The three likely locations for your Mercedes auxiliary battery are the trunk, inside the far left driver's side dash panel, and way up under the front passenger side lower dashboard behind the floor carpeting.
The Mercedes auxiliary battery replacement is quite simple, you just have to unscrew the power leads connected to the auxiliary battery, and replace it with a new Mercedes auxiliary battery.