Key stopped working
Thread Starter
Member
Joined: Oct 2009
Posts: 214
Likes: 38
From: East Idaho
2014 GL450, 2006 S500, 2003 ML350, 1996 C280 (Prev 1995 C220, 2002 CLK320, 1980 300SD Turbo)
Key stopped working
I have a newer key and it was working/synched and it slowly stopped. At first it would take a few tries and unlock would work but lock wouldn't after a while.
I figured it was batteries, changed them out and even did the resynch procedure and still nothing. I tested those same batteries in my other key for the vehicle and they work.
The pins look really clean and doesn't appear to be a contact issue. No water/snow or any exposure like that. Any ideas?
I figured it was batteries, changed them out and even did the resynch procedure and still nothing. I tested those same batteries in my other key for the vehicle and they work.
The pins look really clean and doesn't appear to be a contact issue. No water/snow or any exposure like that. Any ideas?
Member
Joined: Jun 2024
Posts: 191
Likes: 57
E320
Hey RollTideW163, that’s really frustrating when a key fob starts playing hard to get after you thought you had it sorted. Since you've already swapped the batteries and confirmed they work in another key, the issue might lie within the key fob's internal circuitry or the transponder chip. Sometimes, the circuitry can degrade over time, leading to inconsistent performance like what you’re experiencing. Another possibility is that the key fob's antenna isn't communicating properly with your GL450’s receiver, which can prevent certain functions like locking or starting the car even if unlocking still works. If you have access to a diagnostic tool, running a full system scan could help identify any hidden issues that aren’t immediately apparent. I use youcanic full system scanner as it is user-friendly scanner but there are a lot of other options these days. Just make sure it is a good scanner that can perform a thorough all-system diagnostic. If you manage to pull any specific codes, definitely share them here.
Member
Joined: Oct 2018
Posts: 75
Likes: 13
From: Lakewood, Ca
2001 ML 320
I have a newer key and it was working/synched and it slowly stopped. At first it would take a few tries and unlock would work but lock wouldn't after a while.
I figured it was batteries, changed them out and even did the resynch procedure and still nothing. I tested those same batteries in my other key for the vehicle and they work.
The pins look really clean and doesn't appear to be a contact issue. No water/snow or any exposure like that. Any ideas?
I figured it was batteries, changed them out and even did the resynch procedure and still nothing. I tested those same batteries in my other key for the vehicle and they work.
The pins look really clean and doesn't appear to be a contact issue. No water/snow or any exposure like that. Any ideas?
Thread Starter
Member
Joined: Oct 2009
Posts: 214
Likes: 38
From: East Idaho
2014 GL450, 2006 S500, 2003 ML350, 1996 C280 (Prev 1995 C220, 2002 CLK320, 1980 300SD Turbo)
I don't think it's the computer or anything internal on the vehicle, because the old key works. I'm just surprised because this key is fairly new and in seeming new condition. Those four pins the battery sits on look good too.
Any of you ever opened the key up beyond that? I guess I have nothing to lose its just such a pain to have to go to the dealer in Salt Lake Silly to get a stupid 300 dollar key. Maybe they'll mail it.
Any of you ever opened the key up beyond that? I guess I have nothing to lose its just such a pain to have to go to the dealer in Salt Lake Silly to get a stupid 300 dollar key. Maybe they'll mail it.
Member
Joined: Sep 2020
Posts: 91
Likes: 15
From: Arkansas & California
'00 CLK320, '01 ML320 Designo, '01 ML320 Sport; '04 CLK320 Coupe Avantgar; '04 C230 SportCoupe (HB)
RollTideW163,
Which of the 2 distinct functions does not work?
The remote for locking/unlocking, as it seems from your first post.
Or the Key for starting.
From where did you get this new key?
Which of the 2 distinct functions does not work?
The remote for locking/unlocking, as it seems from your first post.
Or the Key for starting.
From where did you get this new key?
Thread Starter
Member
Joined: Oct 2009
Posts: 214
Likes: 38
From: East Idaho
2014 GL450, 2006 S500, 2003 ML350, 1996 C280 (Prev 1995 C220, 2002 CLK320, 1980 300SD Turbo)
The remote locking and unlocking and panic do not work, the blade that is used to start the ignition works. This key doesn't have the infrared light that can be seen with a cell phone camera the way the w202 key has so I can't tell if the signal is even leaving the key, but I am assuming it's not.
Member
Joined: Jul 2019
Posts: 83
Likes: 10
Suzuki cultus, Hond city 2011, Honda city 2003, hopefully and E250 soon
Similar issue on w212 key fob
So initially my key fob had a problem of missing the contact with the cell so I used to wedge something to make it have a better contact and it worked. But after sitting for a while, think 1 month. The key is not working at all, I checked the cell it gave 3 Volts, the contact plates which the cell touches were passing 3 volts too, but when I put it all together the key fob does not work at all, it's small LED light doesn't even blink whenever I click a button, so I tried testing the board too and only a single transistor had some voltage across it, not really sure what's going one, will give a newer cell a shot too, but if anyone has any ideas would love some help on this.
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Member
Joined: Jun 2024
Posts: 191
Likes: 57
E320
It sounds like your ML350's key might be experiencing an internal fault despite appearing physically intact. Given that the battery swap and resynch procedure haven't resolved the issue, it's possible there's a problem with the key's internal circuitry or transponder chip, which could degrade over time or become damaged without evident external signs. The gradual failure you described—working with a few tries to not working at all—could indicate an issue with the signal transmission or the internal microchip, which might have developed a fault that affects its ability to communicate with the car's receiver. It's also worth considering if the vehicle’s receiver or antenna might have a weak spot, although this is less likely given your other key works fine. For a more comprehensive diagnosis, I recommend checking the Central Locking System module, as issues here could sometimes reflect a communication error with one specific key. Scanning this with a full system scanner like youcanic will help identify any non-engine related faults effectively that a basic scanner such as the Launch Creader 3001 might miss. Have you already attempted using this key at different angles or distances to see if there’s any variance in responsiveness? Sometimes subtle changes can indicate where the problem lies.
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Junior Member
Joined: Feb 2023
Posts: 25
Likes: 2
WL163 ML55 and W210 E55
Key EEPROM is worn out
I have a newer key and it was working/synched and it slowly stopped. At first it would take a few tries and unlock would work but lock wouldn't after a while.
I figured it was batteries, changed them out and even did the resynch procedure and still nothing. I tested those same batteries in my other key for the vehicle and they work.
The pins look really clean and doesn't appear to be a contact issue. No water/snow or any exposure like that. Any ideas?
I figured it was batteries, changed them out and even did the resynch procedure and still nothing. I tested those same batteries in my other key for the vehicle and they work.
The pins look really clean and doesn't appear to be a contact issue. No water/snow or any exposure like that. Any ideas?
This means the EEPROM in the key fob is not retaining the memory of the rolling codes for use to unlock properly.
EEPROM has a finite number of writes available before end of life starts kicking in, going back to early 2000's 100k writes was not an uncommon spec.
I had my keys refurbed by a guy who replaced the EEPROM chip in the fobs, I am not sure if this can be done with all keys because it might be some types of key have the EEPROM built in to the processor, don't know.
Junior Member
Joined: Feb 2023
Posts: 25
Likes: 2
WL163 ML55 and W210 E55
So initially my key fob had a problem of missing the contact with the cell so I used to wedge something to make it have a better contact and it worked. But after sitting for a while, think 1 month. The key is not working at all, I checked the cell it gave 3 Volts, the contact plates which the cell touches were passing 3 volts too, but when I put it all together the key fob does not work at all, it's small LED light doesn't even blink whenever I click a button, so I tried testing the board too and only a single transistor had some voltage across it, not really sure what's going one, will give a newer cell a shot too, but if anyone has any ideas would love some help on this.
The key keeps 128 or 256 future rolling codes so if you press the unlock more times between an actual unlocking, than this then the sync can be lost. One way maybe to test is to try locking the car then unlocking to refresh the codes, but see my other post in this thread.
