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Hello, new member here. I hope you are doing well. I have a issue with my c class w204 European model. I was driving it fine went out to the store and then when trying to go back home I noticed my key fob stopped working so I unlocked the car using my physical key and when trying to start the car it would not. I am quite handy and started doing the rounds to try and figure out what's wrong and try to fix it myself.
Symptoms:
key fob stopped working, I can't unlock it remotely (changed the batteries for good measure)
when inserting the key into ignition and turning it on nothing happens
What I did so far: As everything was pointing out to a broken ESL I did the following
battery Ok
radio, lights OK
Central locking ok using the buttons on the door
checked fuses all seem OK
And more:
After looking at the many Mercedes forums I decided to remove the ESL and lo and behold to my surprise no ESL was there to be found. It turns out the car had this issue before and the ESL was replaced with a bypass.
Next thing I was thinking about was replacing the bypass and here is where you guys may be able to help me.
how do I know the bypass is faulty ?
can a broken ESL/BYPASS cause remote unlocking to stop working ?
And lastly here are some photos: No ESL at all Bypass
Dash stays like this - no lights, nothing, fuel gauge doesn't move- even when key is at position 2 is at position 2
I’m not 100% sure if your problem butt I believe you probably should look into a EIS. That is the actual switch you put your key in and turn.
I don't think it's the ESL which is the electric steering lock one because you already have the emulator and because I think when the ESL is bad it will light up the dash and give you a error shown on the display I think.
Search ESL and EIS on the forum here thru advanced search and only search in the W204 section.
I could be wrong tho
Last edited by RobertR728; Apr 16, 2025 at 01:28 PM.
From the limited info i would agree it may be something to do with the ignition lock as it appears it is the control for central locking. I'll try and search around more for something useful.
From the limited info i would agree it may be something to do with the ignition lock as it appears it is the control for central locking. I'll try and search around more for something useful.
Is changing it is as easy as buying a new one and replacing ? or does it also involve key reprograming and what not ?
Sorry I'm not sure if those two modules have any affect on the remote to unlock the doors.
If you get a new fob it will require programming the same with the ESL and the EIS. I would lean more towards the EIS since you already have the ESL emulator.
I never dealt with this issue before. Looking thru the manuals it looks like there is a way to test each separate component.
I am sorry I am not familiar with 889 keykess go option so I can't answer that.
My car is a 2010 model : (204) Berline 180 CDi 2.1 CDI 16V DPF BlueEFFICIENCY 120 cv
Here are some photos
Have you tried scanning the car with a Mercedes specific obd scanner? Since you say the radio and lights come on im assuming the obd port may be functioning.
ESL and EIS failures would not be expected to affect locking. Concurrent failure of two functions points to a failure of a component common to both. The suggestion by @TimC300 to perform a scan with a Mercedes dedicated device is best, because replacing parts without that information can lead to large unnecessary expenses.
I was thinking some more about this issue. I noticed when I open the door the display in the middle of the instrument cluster turns on and shows the vehicle mileage. Without the key in the ignition the middle display is the only thing that comes on.
When you open the door does the middle display turn on? Im guessing no. Makes me wonder if its an issue with the instrument cluster, maybe the fuse. It seems to have its own fuse in the front sam in the engine bay.
How did you check all the fuses, visually or with a multimeter? I would scan the car first for any fault codes. I would also check the fuses, focusing on the instrument Cluster fuse, also it looks like the Ignition Lock and the Electronic steering lock share the same fuse, im seeing two seperate fuses for both of them.
The key fob doesnt work to unlock/lock the doors, but when you press the unlock on the key fob does the fuel filler door unlock? Can you open the trunk using the key fob? Can you open the trunk using the button on the door?
When you insert the key and turn it to On can you hear the fuel pump kicking on under the rear seat? Do the windows and sunroof work?
What voltage are you getting for the battery? Have you tried hooking up a battery charger?
Have you tried scanning the car with a Mercedes specific obd scanner? Since you say the radio and lights come on im assuming the obd port may be functioning.
I was thinking some more about this issue. I noticed when I open the door the display in the middle of the instrument cluster turns on and shows the vehicle mileage. Without the key in the ignition the middle display is the only thing that comes on.
When you open the door does the middle display turn on? Im guessing no. Makes me wonder if its an issue with the instrument cluster, maybe the fuse. It seems to have its own fuse in the front sam in the engine bay.
How did you check all the fuses, visually or with a multimeter? I would scan the car first for any fault codes. I would also check the fuses, focusing on the instrument Cluster fuse, also it looks like the Ignition Lock and the Electronic steering lock share the same fuse, im seeing two seperate fuses for both of them.
The key fob doesnt work to unlock/lock the doors, but when you press the unlock on the key fob does the fuel filler door unlock? Can you open the trunk using the key fob? Can you open the trunk using the button on the door?
When you insert the key and turn it to On can you hear the fuel pump kicking on under the rear seat? Do the windows and sunroof work?
What voltage are you getting for the battery? Have you tried hooking up a battery charger?
I have checked all the fuses using a multimeter
Battery is fine I and I replaced it with a newer one
Volage is 13,8 V
Does this mean that my key is no longer valid ? How is this possible it is the same key I've been using since I bought the car
No. It means the EIS can’t see it. That could mean either the key or the EIS has a malfunction. The EIS usually will display fault codes if it fails. The key can be tested. Many independent shops and some locksmiths have the proper equipment. You have a second key, which also does not work. That would be an unusual situation.
You appear to have the set of conditions to satisfy the Steering/Starting… Diagnostics that @TimC300 sent on 16 April. You have the ESL code A25408. It appears that by that logic, your ESL emulator has failed.
As for the lock/unlock failure, have you changed the batteries in your keys? That function requires fresh batteries.
I am, however, still a bit wary because the two problems seem to have occurred simultaneously. A new emulator may not be extremely expensive, but if it is changed and the problem persists, we are back to a hidden underlying issue.
Does this mean that my key is no longer valid ? How is this possible it is the same key I've been using since I bought the car
No. It means the EIS can’t see it. That could mean either the key or the EIS has a malfunction. The EIS usually will display fault codes if it fails. The key can be tested. Many independent shops and some locksmiths have the proper equipment. You have a second key, which also does not work. That would be an unusual situation.
You appear to have the set of conditions to satisfy the Steering/Starting… Diagnostics that @TimC300 sent on 16 April. You have the ESL code A25408. It appears that by that logic, your ESL emulator has failed.
As for the lock/unlock failure, have you changed the batteries in your keys? That function requires fresh batteries.
I am, however, still a bit wary because the two problems seem to have occurred simultaneously. A new emulator may not be extremely expensive, but if it is changed and the problem persists, we are back to a hidden underlying issue.
No. It means the EIS can’t see it. That could mean either the key or the EIS has a malfunction. The EIS usually will display fault codes if it fails. The key can be tested. Many independent shops and some locksmiths have the proper equipment. You have a second key, which also does not work. That would be an unusual situation.
You appear to have the set of conditions to satisfy the Steering/Starting… Diagnostics that @TimC300 sent on 16 April. You have the ESL code A25408. It appears that by that logic, your ESL emulator has failed.
As for the lock/unlock failure, have you changed the batteries in your keys? That function requires fresh batteries.
I am, however, still a bit wary because the two problems seem to have occurred simultaneously. A new emulator may not be extremely expensive, but if it is changed and the problem persists, we are back to a hidden underlying issue.
Hi, thank you for taking the time to answer. I am willing to buy a new emulator even if it's not a 100% the source of the problem as it is as you mentioned not expensive. I have seen many of those sold as plug and play meaning they don't need programming, is there any truth to that ?
No that's kinda a bait and switch sales tactic.
The new emulator would have to be programmed. You could ask @BenzNinja I think he programs them but I'm not 100% sure he does.
But he is totally reliable and a good person to boot. You can message him on here to find out
Hi, thank you for taking the time to answer. I am willing to buy a new emulator even if it's not a 100% the source of the problem as it is as you mentioned not expensive. I have seen many of those sold as plug and play meaning they don't need programming, is there any truth to that ?
I have never seen a plug and play emulator. ESL, EIS, TCU, ECU all need to be married together to satisfy the requirements of the Drive Authorization System (DAS) or the car is not going anywhere.
So I noticed that my ESL emulator light doesn't turn green and is always red.
Is that a definitive sign that it's broken ?
Also can I use the starter relay trick to jump start it ?
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