Auxiliary battery malfunction

You will need to replace the auxiliary battery located in the trunk area. I've attached pictures with instructions.

I have check the trunk, but it's not in there.

Then yours may be mounted in the dash on the driver’s side. It’s the size of a power wheels battery, super small. The panel at the driver side knee area and the small panel on the left side of the dash accessible when you open the door, pop the panel out and remove the 10mm bolt and the battery will drop down so you can grab it from below the dash. Some E classes have it in the trunk area and some on the driver side dash area.

Hello, just wanted to jump in as well. As BMDOUBLE stated earlier, the auxiliary battery should be in the luggage compartment. Mercedes gives a poor diagram as to the exact location but it looks like you will need to remove the trim covers to actually see it?

I would recommend you get an advance scan tool and do a full system scan to see what codes may be posted. Once you have those codes we can further assist. Also when I mention a scan, I do not mean those quick scans you get from the parts stores. You only get engine and maybe ABS codes. I am talking about a full scan where it scans every module in your vehicle.

Let us know if you find the auxiliary battery after removing all panels in trunk or if you can get the whole computer system scanned.

Yea, I looked it up and it looks like it might be under the driver side dash.

It's a 2010 e350 4matic.

Does it have to be a Mercedes battery? Because they have them at battery's plus but the are Duracell.

As long as it’s the same physical size and volts, it will work.

Okay, it's a little smaller and more volts. Is that okay?

Volts or amp hours? it needs to be 12 volts.

Is it okay to drive it until get the battery?

Yes you can still drive it.

Good, because I haven't driven it for weeks now. tired of driving my truck. just got to get that battery now.. thanks

Roger that!

I was facing the same issue and came across this blog, it also helped me a lot to identify where auxiliary battery is located and how to install it.

https://xenons4u.co.uk/blog/mercedes-benz-auxiliary-battery-malfunction-explained/