2014 E350 Auxiliary Battery Malfunction
MBWorld Fanatic!
Joined: Mar 2014
Posts: 3,107
Likes: 394
From: West Central Florida
2011 E550 P2 4M Sedan
https://mbworld.org/forums/e-class-w...ml#post5855871
See the post linked above for pdf with photos.
See the post linked above for pdf with photos.
Member
Joined: Aug 2016
Posts: 245
Likes: 105
2014 E350
Edward
Junior Member
Joined: Jul 2014
Posts: 65
Likes: 2
2014 E250 Bluetec
It makes you wonder if not using ECO will prevent this battery from needing changing that often. It doesn't make sense to save a few pennies using ECO if it ends up costing hundreds in service calls. Now, if I can only find a permanent ECO bypass.
MBWorld Fanatic!
Joined: Jul 2008
Posts: 8,384
Likes: 800
2019 G70 6MT & 2022 Ford Maverick XL
Member
Joined: Nov 2016
Posts: 88
Likes: 13
From: Long Island, NY
2014 Mercedes Benz E350 Sport 4matic
Battery is in the trunk in the spare tire well. This only affects ECO start/stop and the brake hold function.
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
Likes: 1,550
From: MA
2008 E350 4Matic, 2011 E350 4matic
It makes perfect sense. Eco mode will give you better gas mileage and allows MB to hit their CAFE numbers which is mandated by the government. Costing you hundreds in service calls isn't a factor in CAFE numbers. It's a WIN-WIN for MB, better CAFE numbers and extra revenue for their dealers. A little bad PR from owners that complain, but that's their cost of doing business.
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Super Member
Joined: Feb 2013
Posts: 580
Likes: 62
From: Maryland
2013 E550 4Matic
Member
Joined: May 2012
Posts: 96
Likes: 2
2007 E63 AMG
Anyhow, my car just threw the same "Aux Bat Malfunction" message yesterday. After that, I noticed that not only auto hold is gone, distronic plus cruise is gone as well. I wonder if this means auto emergency stop, front cross traffic alert/assistance, etc are gone as well?
Local MB dealer has been a bit of pain to get an appointment for this, kept telling me to just come in before 2pm and wait for it (no loaner, not taking appointment for this apparently). Basically forcing me to lose at least a couple of working hours.
Newbie
Joined: Jan 2017
Posts: 14
Likes: 1
From: Dallas
E350
Just got this replaced under warranty at my local MB dealer. I asked him what it does. He said it operates the ECO and it also is a backup to the main battery so that if your main battery dies you can still get the car in Neutral so that you can get the car out of the garage to get a jump/on a tow truck/or whatever. I don't know how much it costs and it appeared to be in the trunk of my 2014 E350 as they had that open at one point when it was in the service bay.
Newbie
Joined: Sep 2012
Posts: 10
Likes: 2
From: Columbus, Ohio
2014 E350
Auxiliary Battery Malfuction
Had the same problem at 23186 miles. It was corrected by the dealer in Columbus Ohio by replacing the auxiliary battery in the truck at no cost. Also got a free car wash.
MBWorld Fanatic!
Joined: Feb 2004
Posts: 1,001
Likes: 37
From: NY
2014 E350 4Matic
Same here. At about 25k miles the auxiliary battery on my '14 E350 went. The dealer replaced it under warranty in less than 30 min. in and out the door. No problems since. About 5 months before it failed, I had, however, as a precaution, charged that battery to full capacity. Apparently, some early batteries were no good, period.
Super Member
Joined: Sep 2008
Posts: 627
Likes: 33
From: SF
E-Class
Ill just add to it: 2014 E350 23k miles and had a malfunction message upon pick up from used dealership. Had MB replace it under warranty about 9 months prior to expiration.
As above, lots of functions ceased to function - hold/hill assist, park assist.
As above, lots of functions ceased to function - hold/hill assist, park assist.
Newbie
Joined: Nov 2017
Posts: 1
Likes: 0
mercedez E350
Hi I’m own a E350 and i just miss the warranty for a mont on the same problem with the auxiliary battery
and the estimated price is 370 dollars in the dealer it is expensive but i need to doit i dont want this problem to afect any other aistem in the car
but if it helps to keep the eco thing off i will thanks my car has 39k miles
and the estimated price is 370 dollars in the dealer it is expensive but i need to doit i dont want this problem to afect any other aistem in the car
but if it helps to keep the eco thing off i will thanks my car has 39k miles
MBWorld Fanatic!
Joined: May 2015
Posts: 4,037
Likes: 1,011
From: Miami, FL
2003 CL 600
Hi I’m own a E350 and i just miss the warranty for a mont on the same problem with the auxiliary battery
and the estimated price is 370 dollars in the dealer it is expensive but i need to doit i dont want this problem to afect any other aistem in the car
but if it helps to keep the eco thing off i will thanks my car has 39k miles
and the estimated price is 370 dollars in the dealer it is expensive but i need to doit i dont want this problem to afect any other aistem in the car
but if it helps to keep the eco thing off i will thanks my car has 39k miles
Senior Member
Joined: Apr 2016
Posts: 457
Likes: 151
From: Phoenix, AZ
2016 E350 Sport 2WD
This battery is a very common failure on all the eco mode equipped cars. Normally, it fails the internal resistance check, it's not that the battery is bad yet. Most of them when I test them after removal have 13+ volts and show as a very good battery, but once the internal resistance is over 1.76 Ohms, it fails and has to be replaced. Will be a PITA once out of warranty, but any normal powersports battery that size could be used, it doesn't have to be some special MB battery, although it must be sealed.
Super Member
Joined: May 2014
Posts: 620
Likes: 65
From: Florida
2018 E300 Luxury - P3 and more
My 2015 E350's been through THREE of these batteries in 48k miles. I also had one of the service loaners throw up an Aux Battery Failure at 4k miles too. Definitely a design flaw.
Senior Member
Joined: Jul 2010
Posts: 269
Likes: 3
2014 W212 E350 4M
This battery is a very common failure on all the eco mode equipped cars. Normally, it fails the internal resistance check, it's not that the battery is bad yet. Most of them when I test them after removal have 13+ volts and show as a very good battery, but once the internal resistance is over 1.76 Ohms, it fails and has to be replaced. Will be a PITA once out of warranty, but any normal powersports battery that size could be used, it doesn't have to be some special MB battery, although it must be sealed.
MBWorld Fanatic!
Joined: Jun 2017
Posts: 1,334
Likes: 766
2020 GLS450 (wife) / 2024 Ford Bronco (mine) / 2014 VW Tiquan (son)
Mine has gone out now too (2014 at 32k miles). Mine is in the trunk. I’m ready to replace it (out of warranty, not a CPO item), but can’t figure out the part number.
Anyone know this part number by chance? My dealership won’t tell me (probably because they want me to buy it from them for $300 for just the battery).
this is mine.
Thanks!
Member
Joined: Apr 2010
Posts: 79
Likes: 3
From: Edmond, OK
2014 E350 4MATIC, 2013 SL550
Old thread but my aux battery errored today. Local dealer wanted $379 including installation or $187 including tax for the part. I ordered the OEM part online delivered for $125. Took 10 minutes to install. Folks of your vehicle is out of warranty, do this install yourself and save the money.
