I just changed one the other day and the car still had the message, changed it again and away it went 
Replace key battery
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Senior Member
Joined: Mar 2018
Posts: 356
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From: Elizabethtown Kentucky
2019 E 300 4matic 2013 SLK 250
Replace key battery
Got the “replace key battery” warning in the MFD on Monday. I replaced the battery and had 24 hours without the warning. Today I went to start the car and the battery warning popped up again.
any idea what’s wrong?
any idea what’s wrong?
Last edited by DeutscheBenz726; Dec 23, 2020 at 12:45 PM.
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From: Silicon Valley, USA
No AMG unfortunately, and we'll just leave it as that
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2012 E350 sport suspension; 2014 Lexus RX 350
Replace Key Battery
I get the replace MFD message and it hasn't gone away after replacing the battery. I checked the new battery and it's 3.2V, and the key starts the engine and unlocks the doors and trunk lid just fine. Would the recent change in weather (colder) have anything to do with it? The temp was in the 20's overnight, and was around 35 when I started the car this morning. It's still cold midday, around 35 degrees.
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From: Austin, TX
2013 SL550 BiTurbo
I get the replace MFD message and it hasn't gone away after replacing the battery. I checked the new battery and it's 3.2V, and the key starts the engine and unlocks the doors and trunk lid just fine. Would the recent change in weather (colder) have anything to do with it? The temp was in the 20's overnight, and was around 35 when I started the car this morning. It's still cold midday, around 35 degrees.
My Wife's key was setting off my indicator on the E. She didn't even drive, just parked next to me in the driveway...
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2012 E350 sport suspension; 2014 Lexus RX 350
nota_amg, I see how that worked in your circumstance -- clever to figure that out. It's not the problem with mine. My other key is not in use and is protected inside a shielded pouch from activation by malign actors (car thieves)..
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From: Dallas-Ft.Worth,TX
2016 E350 Sport
Super Member
Joined: Nov 2011
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From: Austin, TX
2013 SL550 BiTurbo
yeah, that one threw me for a loop and had me scratching my head for a few days.
Even if it is hidden away, might not be a bad idea...just to rule it out...you never know. Maybe you bag isn't working...
Even if it is hidden away, might not be a bad idea...just to rule it out...you never know. Maybe you bag isn't working...
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From: Austin, TX
2013 SL550 BiTurbo
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From: Pepper Pike Ohio
24 GLS580 '23 E450 4matic 12 E350 4Matic
Since Marvin is moving from trunk lid to bumper, we may have to get him a housewarming gift!
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From: Dallas-Ft.Worth,TX
2016 E350 Sport
Well...
Well...
Well, I may have a few Faraday Cage bowls sitting around. But I do NOT keep a handful of 2025 batteries and a voltmeter in the center console. OK?
Well...
Well, I may have a few Faraday Cage bowls sitting around. But I do NOT keep a handful of 2025 batteries and a voltmeter in the center console. OK?
Super Member
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From: Austin, TX
2013 SL550 BiTurbo
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From: Marin County,California
2016 E350 Sedan
Don't laugh My house has a stucco exterior which is installed over metal lath (I guess to give it strength) . My entire house has become a faraday cage. Great for key remotes. Not so good for cell phone reception.. I have to stand near an open door or window to get a good signal.
Last edited by Alandf; Jan 27, 2021 at 04:41 AM. Reason: spelling
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2012 E350 sport suspension; 2014 Lexus RX 350
FobGuard Security Pouch - Ideal Faraday Cage to Protect Car Keyless Entry Fobs from Hacking, Signal Amplification and Signal Relay Attacks
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From: Dallas-Ft.Worth,TX
2016 E350 Sport
Bowls not necessary:
Brand: FobGuard
FobGuard Security Pouch - Ideal Faraday Cage to Protect Car Keyless Entry Fobs from Hacking, Signal Amplification and Signal Relay Attacks
Brand: FobGuard
Have you tested it? Cause it DOESN'T Work.
Before we drift far afield again, check out this thread... https://mbworld.org/forums/e-class-w...ml#post7868809
Last edited by DFWdude; Jan 26, 2021 at 09:11 PM.
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From: Dallas-Ft.Worth,TX
2016 E350 Sport
But no one places only their primary key fob in the pouch, because it is almost always attached to other keys (house/apartment key, other car keys) and items on key ring(s) that dangle outside the pouch. Tried this way it will never work, because the extra items work as an antenna outside the pouch and the flap can never be completely sealed. Not very practical for a daily use key fob.
Last edited by DFWdude; Jan 27, 2021 at 01:07 PM.
