bumparker

2014 E350 with 30,000 miles giving the above message on start-up. The dealer covered the battery replacement under warranty. I thought I would give some information on this battery as information appears to be scarce on the forums. I first suspected the battery in the trunk would be the auxiliary battery but I was wrong. There is a battery in the dash (driver side). I did not see the actual battery (but it would be the size of something you could hold in your hand). Apparently you need to remove a lower dash panel and the panel on the side of the dash (which you can only access with the door open) in order to access and replace the battery. I could never find a good part number reference on-line nor get a good estimate of the cost of the battery. The cost didn't matter this time but the battery went bad after 18 months so I may face this issue again when the car isn't covered by warranty. If anyone has additional information for the forum please share.

konigstiger

ECO start/start battery

bumparker

Konigstiger,

Thanks for posting the info. This info is for the Eco start-stop battery in the trunk. There is another smaller battery in the dash. The battery in the dash is the one causing the error message. It was hard to find much information on the battery in the dash.

KEY08

That is for the electronic shift mechanism.

konigstiger

MY14 has starter battery (10) & ECO battery (500) EPC shows it does not have a battery in the dash (400 is grayed out).

bumparker

I was out of town when my wife took it took the dealer. The dealer told her they replaced the battery in the dash. Maybe they gave her the wrong information. I'll have to look at the battery in the trunk and see if it appears to have been replaced.


I guess it is a mystery, is there a battery in the dash of a 2014 E350 or isn't there????

bumparker

I think things make more sense now. I looked in the trunk and it appears the battery has been replaced. I guess the service adviser just gave my wife the wrong location. I am assuming there isn't a battery in the dash. Thx for the help.

parodielin

This happens with SAs all the time. Sales are even worse. I talked to one of the big shot benz dealer sales and he did not know the difference between standard LED lights and Adaptive LED lights on 2014 E350.


My key programming issue is also very confused for many of them.


Do we know how the aux battery is charged? I charged my main battery using CTEK trickle. I don't think I can charge the battery in the truck directly. The connectors weren't obvious... Is there an aftermarket part for this?

konigstiger

Read post 2 attachment in its entirety.

MPTLPTR

Do you turn off ECO start/stop usually?

I have a 2014 E350 w/~20,000 miles and had the same issue. My dealer also replaced the ECO start/stop battery in the trunk to "fix" it. I almost always turn off the ECO start/stop and am thinking that may have contributed to the early demise of the battery.

BACnMercedes

So does this warning control the transmission or the eco start stop. I've read the transmission but when I called the dealer they said it controlled the economy start stop and therefore the only problem woupdate be that it, the eco start stop, will not work.
So here is the question. I hate the eco start stop and always turn it off. So if this "auxiliary battery malfunction" only controls the eco start stop and doesn't hurt anything, why change the battery? By not changing the battery, I never have to turn that dang eco start stop feature off.
Thanks

Royce118

This will also affect the brake hold function.

BACnMercedes

Thanks. So I assume you mean the hold feature when you're stopped somewhere and you press the brake really fast and the "hold" light appears and you can remove your foot from the brake and the car will not move till you press the gas. My wife does not use this feature in the E but I do when I drive it. But does it also affect the brake hold feature to where the car stays stopped for about a second while you remove your foot from the brake and apply the gas? Just curious and trying to figure everything outhat that this battery controls.
Thanks

Liam1234

My 2014 E350 had the same failure at around 18k miles. Fixed under warranty. It looks to be a might expensive battery.

Edward993

My '14 E350 threw up the malfunction light last month at 21k miles, and was likewise replaced under warranty. Yes, both the ECO function failed (thankfully), as did the "Hold" which I actually like. I hope the battery actually lasts this time as it seems premature to fail. But given its silly sole function (if I understand its function correctly), I doubt I'd replace this battery in the future if it's a costly replacement.


Edward

mikerx80

Had the same problem for my 14 at 16k miles. I believe it is a modest fix. But the Dealer fixed under warranry. Where is the hold button and was it an option?

Liam1234

mikerx80,

it is a hold function... (no button)

start car up and then press the brake, press even further and this will enable the hold function..,you will see the word "HOLD" in the dash when you do this. you can now take your foot off the brake and the car will still be in brake mode (as in it will not go anywhere)

useful for hill starts i guess? in traffic and sick of keeping your foot on the brake? thats what I use it for...

mikerx80

So does this work only at start? I tried this a few times at stops and the engine just starts right up when in eco or just keeps going if on regular yellow "eco" mode.

Liam1234

Vidoe link of the HOLD function

https://www.mbusa.com/mercedes/owner...007c184335RCRD

AllenOU

Same problem with my 14 at 35k miles. haven't had an issue in the last 5k after replacement

thephantom

I also had the same issue last November in my 14 with around 15K miles. I was also told the Aux battery is in the dash. 11 months and 11K miles later all seems well.

Munich77

I had mine replaced under warranty in August - it is indeed expensive.

ItalianJoe1

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.

drcookie

Thanks for the info.

My 2014 E350 started to display the message this morning on the dashboard. The car is 31k miles. I guess I need to make an appointment with the dealer today.

divaboy

I'm having this same issue on my car. Can anyone tell me the exact place where I can find the battery, booth or dash? Pictures will be highly appreciated.

Also, I noticed the HOLD function on the braking system is no longer working. What else is affected?

Thanks