How to fix Auxiliary Battery Malfunction on Mercedes S550 w221

In this video I answer these questions:
What is the Auxiliary battery used for?
Why does it fail? How to replace it?

The video has a link to an aftermarket Aux Battery for a less expensive option

If you'd like to jump right to the answer:

00:00 Intro
00:49 What is the Auxiliary Battery used for?
01:30 Why is the "Auxiliary battery malfunction" message displayed?
02:21 How to replace the Auxiliary Battery?

This is the same repair process for all 2007 2008 2009 2010 2011 2012 and 2013 Mercedes-Benz S550 w221.

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Jamie is the Owner of some auto repair shops in Sarasota Florida, Check out his social media in the links below:
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[LupeMoya]

This battery does way more than just switch the transmission in an emergency. Once I replaced mine, the error message disappeared and my parking brake, parking sensors and the hold in drive feature started to work normally again. Great video!

[michelmiami]

Thank you! Just saved $350 because of your video. This was awesome.

[charlesdove]

Great video! My Auxiliary Battery Malfunction light came on this morning on my 2013 S550. I figured this was the trunk battery. I'm so glad that I googled the error message and found your video. I will get a new Mercedes Auxiliary Battery and replace it myself - excellent detail with easy to follow directions. I really appreciate this.

[kawansmith]

Thank you so much!!! You are the only person on YouTube and the dealer that showed me how to do this!

[KM-bvfp]

Very thorough. Appreciate your diagnostic tips but especially the explination of the purpose of the battery as I was considering just driving it until you pointed out that if you need a tow you could be screwed

[khyrovancho]

YouTube have save us so much money especially on cars, I learn to change auxiliary battery by watching videos

[vinnievegas]

AWESOME video! Excellent on the detail. Keep it up. Did the one on my 2012 S550 W221 exactly the same.👍

[darrelpetrie]

Excellent detailed instructions. I have a 2011 CL500 W216 (Australia) and no where in the manual can I find there is an aux battery but, it is there!

[NumairAidroos]

Thank God for your video. Daimler India, in our region is on a shortage, and this battery has to be ordered from Germany or Taiwan, I had one from a Robotics project, it was plug and play.

[larrydunn]

thanks. worked just as you showed on a 2011 S550. Ordered battery OEM from Amazon for $47.29, and start to finish install was 45 minutes... only because I was slow and careful. You don't need a 10mm wrench... a needle nosed vise grip worked for me b/c my 10mm socket didn't fit int he space allotted. I already had a 25mm torx from years ago when I needed to remove a Mercedes door panel. I used a painter's multitool, the part with about 5/8" dull blade, to work the side panel off. As you showed, the red connector is harder to get off the old battery than the black side.

On a side not, we have had many MB... 190E, C280, E320, of the S Class, W140 x2, W220 (worst car EVER), and now W221. The 221 is the most trouble free of any car we've ever owned, with 160, 000 miles and going strong.

[Ari-eg]

Thank you for your video's. I learn alot from you! Nice clean job👍

[ObiJuan]

Very nice video and right to the point. Can you post link where to order factory battery from? Thank you.

[kenchagee]

Great Video !!!! I just cancelled my appointment to have it fixed. I figured hell Id give it a try (with the after market part of course since it was cheaper) Amazon delivered it in one day, however I forgot to get and didn't have a 10mm wrench. I made it work with some pliers and my fingers. But the message is gone, If it comes back I'll try the OEM part but until Thx a million !!!

[Dcs-Brasil]

Very good! I'm here cause Humble Mechanic! Thx Jamie...

[jasimjasim]

Thank you so much

Easy to explain
Clear video
Easy to replace the battery

Thank you

Jasim .. from Kuwait

[ShawnD]

Thank you for the great video. I have a 2011 S550 my main battery went back 3 months ago. I wish they had replaced the Auxiliary battery then.

[robertociletti]

Very usefull!
Good quality of viseo and sound. Explanation clear.

[dionipedales]

Nice job !! It will help me to change it . Greetings from Spain !!😊

[conradharman]

Thanks, really well done video. I had this flash up the other day but it went away. I presume it just discharged as it was -23. May still replace as preemptive maintenance.

[AutoEuropeCars]

Thank you for detail video and instruction 👍👍