SmartKey Issues
Thread Starter
Junior Member
Joined: Jul 2023
Posts: 68
Likes: 16
From: West Coast US
E350 (W212)
SmartKey Issues
Currently having a weird issue with my key/car:
No button on the keys work; the unlock, lock, trunk, or panic button, none work. Starting the car does not work. No lights on the gauge cluster at all when inserting or turning the key.
I ended up opening the car with the physical key blade and of course the alarm sounded, and I tried to start the car with the key but nothing happened, so I ended up opening the hood and disconnecting the 12V battery to stop the alarm for the time being.
The only indication of anything I saw was a small red flash when I pressed the lock button next to the panic button indicating the key battery is ok. Car battery is ok, hazards work and it's at 12.6 volts.
Do I need a new key?
No button on the keys work; the unlock, lock, trunk, or panic button, none work. Starting the car does not work. No lights on the gauge cluster at all when inserting or turning the key.
I ended up opening the car with the physical key blade and of course the alarm sounded, and I tried to start the car with the key but nothing happened, so I ended up opening the hood and disconnecting the 12V battery to stop the alarm for the time being.
The only indication of anything I saw was a small red flash when I pressed the lock button next to the panic button indicating the key battery is ok. Car battery is ok, hazards work and it's at 12.6 volts.
Do I need a new key?
Last edited by DBSeer; Nov 30, 2025 at 03:36 PM.
MBWorld Fanatic!
Joined: Jan 2016
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From: In the Shadow of the Tetons
2013 ML350 Bluetec
A new fob battery sounds warranted. You should be able to turn the car alarm off after getting in with the metal key by starting the car with the fob- that is, pop the keyless go button out, stick in the key fob and start the car.
Thread Starter
Junior Member
Joined: Jul 2023
Posts: 68
Likes: 16
From: West Coast US
E350 (W212)
I have tried a new battery, doesn't change anything. Looking it up, the red flash on the key seems to indicate that it's getting power, so I think the key battery isn't an issue.
That being said, after reconnecting the battery, there is nothing at all when I insert/turn the key into the ignition switch, no indication of anything on the gauge cluster, no noise, nothing.
That being said, after reconnecting the battery, there is nothing at all when I insert/turn the key into the ignition switch, no indication of anything on the gauge cluster, no noise, nothing.
Thread Starter
Junior Member
Joined: Jul 2023
Posts: 68
Likes: 16
From: West Coast US
E350 (W212)
I think I might be needing a new key, so I called around and I'm even more disappointed:
- Dealer says $700 and the car needs to be there (so I need to get it towed 30 miles to the dealer so more like $1000)
- Almost every independent locksmith I called said their couldn't do it, one guy said he could do it for $650 but I think he might be lying
Does anyone know of any mobile service that can do key replacements? Better yet something other than the stealership?
- Dealer says $700 and the car needs to be there (so I need to get it towed 30 miles to the dealer so more like $1000)
- Almost every independent locksmith I called said their couldn't do it, one guy said he could do it for $650 but I think he might be lying
Does anyone know of any mobile service that can do key replacements? Better yet something other than the stealership?
Super Member
Joined: Oct 2012
Posts: 538
Likes: 89
From: Hollywood, CA
W209, W124
Curious what “inserting or turning the key “ means. Is it actually turning?
little red light typically is a sign key is functioning at some level
can aim at phone camera and check for IR flash when button pushed
2014 and later is dealer only
little red light typically is a sign key is functioning at some level
can aim at phone camera and check for IR flash when button pushed
2014 and later is dealer only
Banned
Joined: Nov 2025
Posts: 477
Likes: 187
From: US
Mercedes SL R231
I think I might be needing a new key, so I called around and I'm even more disappointed:
- Dealer says $700 and the car needs to be there (so I need to get it towed 30 miles to the dealer so more like $1000)
- Almost every independent locksmith I called said their couldn't do it, one guy said he could do it for $650 but I think he might be lying
Does anyone know of any mobile service that can do key replacements? Better yet something other than the stealership?
- Dealer says $700 and the car needs to be there (so I need to get it towed 30 miles to the dealer so more like $1000)
- Almost every independent locksmith I called said their couldn't do it, one guy said he could do it for $650 but I think he might be lying
Does anyone know of any mobile service that can do key replacements? Better yet something other than the stealership?
A locksmith might be able to code your fob if you have a 2014 or older car, and not all 2014s either. The process is somewhat involved to sync the fob with the car. Anything newer and you have to go to the dealer with proof of ownership.
Thread Starter
Junior Member
Joined: Jul 2023
Posts: 68
Likes: 16
From: West Coast US
E350 (W212)
Yes there is IR light upon pressing a button. It's later end 2014 E350 unfortunately. It's going in the ignition cylinder and turning just fine, normal, but with exactly no response from the car.
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Thread Starter
Junior Member
Joined: Jul 2023
Posts: 68
Likes: 16
From: West Coast US
E350 (W212)
You haven’t told us anything about your car. Which model and year?
A locksmith might be able to code your fob if you have a 2014 or older car, and not all 2014s either. The process is somewhat involved to sync the fob with the car. Anything newer and you have to go to the dealer with proof of ownership.
A locksmith might be able to code your fob if you have a 2014 or older car, and not all 2014s either. The process is somewhat involved to sync the fob with the car. Anything newer and you have to go to the dealer with proof of ownership.
Proof of ownership shouldn't be an issue but what's really annoying is they want the car at the dealer. Towing a fully functional car feels like such a waste just to have them to plug in their xentry tool for 30 seconds or whatever.
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Super Member
Joined: Oct 2012
Posts: 538
Likes: 89
From: Hollywood, CA
W209, W124
I don’t know about 2014 but in my 2005 the only time the EIS can turn is if key has already been accepted. So these symptoms on my car would mean bad EIS. (Or dead battery)
Do you have a key to a different car you can try? Curious if by 2014 they just let the EIS spin no matter the key.
Do you have a key to a different car you can try? Curious if by 2014 they just let the EIS spin no matter the key.
Thread Starter
Junior Member
Joined: Jul 2023
Posts: 68
Likes: 16
From: West Coast US
E350 (W212)
I don’t know about 2014 but in my 2005 the only time the EIS can turn is if key has already been accepted. So these symptoms on my car would mean bad EIS. (Or dead battery)
Do you have a key to a different car you can try? Curious if by 2014 they just let the EIS spin no matter the key.
Do you have a key to a different car you can try? Curious if by 2014 they just let the EIS spin no matter the key.
I wish I had another key to troubleshoot with but I unfortunately only have one.
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
Likes: 6,802
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
HELP GUESSING RIGHT
You are now reaching in the thousand dollar repair for your keyfob.
MB dealership network can provide timely service.
Perhaps you could use a $150 OBDII Launch scanner to research what your chassis is doing?
The solderless Electronic Ignition Slot would be a module to scrutinize for live status. At this stage we have gone passed the marginal KeylessGo trunk module.
Use a smart charger to help both your batteries not get flat.
MB dealership network can provide timely service.
Perhaps you could use a $150 OBDII Launch scanner to research what your chassis is doing?
The solderless Electronic Ignition Slot would be a module to scrutinize for live status. At this stage we have gone passed the marginal KeylessGo trunk module.
Use a smart charger to help both your batteries not get flat.
Last edited by CaliBenzDriver; Dec 1, 2025 at 12:42 PM.
Thread Starter
Junior Member
Joined: Jul 2023
Posts: 68
Likes: 16
From: West Coast US
E350 (W212)
I have a pretty nice scan tool that I will try using soon, not sure how it will work with the fully off. Sucks that the dealership is the only option, if it happened like a month after this point I'd be slightly less disappointed as at least I could get my 500k badge at the same time!
I will try one more thing though; there is a common issue with these key fobs that consists of BGA chip solder ball being loose, I am not super experienced with these tiny electronic repairs but I'll still give it a shot because worst case scenario, I go from all keys lost to all keys lost, best case, I now have another key that I might be able to do drive to the dealer with.
I will try one more thing though; there is a common issue with these key fobs that consists of BGA chip solder ball being loose, I am not super experienced with these tiny electronic repairs but I'll still give it a shot because worst case scenario, I go from all keys lost to all keys lost, best case, I now have another key that I might be able to do drive to the dealer with.
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
Likes: 6,802
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
DO OBVIOUS FIRST
I have a pretty nice scan tool that I will try using soon, not sure how it will work with the fully off. Sucks that the dealership is the only option, if it happened like a month after this point I'd be slightly less disappointed as at least I could get my 500k badge at the same time!
I will try one more thing though; there is a common issue with these key fobs that consists of BGA chip solder ball being loose, I am not super experienced with these tiny electronic repairs but I'll still give it a shot because worst case scenario, I go from all keys lost to all keys lost, best case, I now have another key that I might be able to do drive to the dealer with.
I will try one more thing though; there is a common issue with these key fobs that consists of BGA chip solder ball being loose, I am not super experienced with these tiny electronic repairs but I'll still give it a shot because worst case scenario, I go from all keys lost to all keys lost, best case, I now have another key that I might be able to do drive to the dealer with.
The instrument cluster does not need to be fully ON for the chassis to already be powered up.
The scanner CAN-D talks to the SAM's and CAN-B that are always powered ON anyway.
