Smart Key not detected
Thread Starter
Newbie
Joined: Mar 2022
Posts: 10
Likes: 2
2013 E350, 2020 SL450 R231
Smart Key not detected
Has anyone had success in diagnosing and resolving the display message "Key Not Detected"? The message requires one to insert the physical key fob into the ignition slot to start the car. All other functions (lock, unlock) seem to work fine.. I've tried several resolutions. I've changed batteries, tried different Smart Keys, re-synced each key fob - all with no luck. Additionally this issue does not happen 100% of the time, I would estimate about half the time. I've tried to isolate different environment conditions - but there seems to be no consistent common thread to the problem. Car is a 2013 E350 Coupe. Any thoughts please..
Super Member
Joined: Jul 2017
Posts: 517
Likes: 59
2012 E550 Cabriolet 2011 VW Eos 1985 Pininfarina Spider
Has anyone had success in diagnosing and resolving the display message "Key Not Detected"? The message requires one to insert the physical key fob into the ignition slot to start the car. All other functions (lock, unlock) seem to work fine.. I've tried several resolutions. I've changed batteries, tried different Smart Keys, re-synced each key fob - all with no luck. Additionally this issue does not happen 100% of the time, I would estimate about half the time. I've tried to isolate different environment conditions - but there seems to be no consistent common thread to the problem. Car is a 2013 E350 Coupe. Any thoughts please..
Super Member
Joined: Nov 2017
Posts: 669
Likes: 142
From: Hermosa Beach, California
2018 E400 Coupe
Several years ago a local repair shop lost our only FOB for my wife's 1999 C230. They initially acted like it was my problem, but after I threatened to sue them, they managed to find one that was made by some company other than MB. IIRC, they found it at a local key shop. In any event, they were able to configure it to work with her car. Wouldn't hurt to ask around.
Super Member
Joined: Jul 2017
Posts: 517
Likes: 59
2012 E550 Cabriolet 2011 VW Eos 1985 Pininfarina Spider
Several years ago a local repair shop lost our only FOB for my wife's 1999 C230. They initially acted like it was my problem, but after I threatened to sue them, they managed to find one that was made by some company other than MB. IIRC, they found it at a local key shop. In any event, they were able to configure it to work with her car. Wouldn't hurt to ask around.
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
Likes: 6,776
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
UNSTABLE KEYLESS MODULE
Has anyone had success in diagnosing and resolving the display message "Key Not Detected"? The message requires one to insert the physical key fob into the ignition slot to start the car. All other functions (lock, unlock) seem to work fine.. I've tried several resolutions. I've changed batteries, tried different Smart Keys, re-synced each key fob - all with no luck. Additionally this issue does not happen 100% of the time, I would estimate about half the time. I've tried to isolate different environment conditions - but there seems to be no consistent common thread to the problem.
Car is a 2013 E350 Coupe. Any thoughts please..
Car is a 2013 E350 Coupe. Any thoughts please..
Consider these steps:
-1- Use a scanner to survey and clear all unstable modules gone wild, a 5mn procedure.
-2- Reboot chassis to sanitize silently unstable CAN module such as sleepless CGW.
The keyfob could be bad, but unlikely.
When batteries are discharged this helps make long-distance rear modules more unstable (KeykessG)... float-charge up your batteries with a CTEK or NOCO.
So it's not one item you need to deal with but an array of marginal conditions that need to be sanitized + prevented.
+++ COIN CELL...
Not to overlook the obvious: the key fob battery can get drained and is easily replaced.
Last edited by CaliBenzDriver; Aug 2, 2025 at 11:50 AM.
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Junior Member
Joined: Mar 2012
Posts: 35
Likes: 6
From: Treasure Island, Florida
2011 E550 Cabriolet
Several years ago a local repair shop lost our only FOB for my wife's 1999 C230. They initially acted like it was my problem, but after I threatened to sue them, they managed to find one that was made by some company other than MB. IIRC, they found it at a local key shop. In any event, they were able to configure it to work with her car. Wouldn't hurt to ask around.
Super Member
Joined: Nov 2017
Posts: 669
Likes: 142
From: Hermosa Beach, California
2018 E400 Coupe
RealDonn — I have no idea, and although that location is still a shop, it's under a different name, different owner, different crew, which is hardly surprising. I mean, how can a mechanic work on a car, moving it in and out of the garage, move it to the parking lot, and then lose the key (or FOB in this case)? Morons rarely stay in business for long (can't say the same about politicians, unfortunately).
BTW, the replacement FOB looked significantly different from the original MB fob — it was black, for one thing, and a bit larger — but it worked.
BTW, the replacement FOB looked significantly different from the original MB fob — it was black, for one thing, and a bit larger — but it worked.
Last edited by The_Judge; Aug 4, 2025 at 10:46 AM.
