When starting the car

the key gets its power from the inductive process from the cars battery.
Either your key battery is making poor contact or the key is failing.
Check and clean battery contacts in the key.

 

Just replace the batteries in the key.

 

If the red light on the key fob comes on when you press the lock/unlock button then the battery is fine.

The key has two components to it. A radio frequency component that operates the locking/unlocking of the car and an infrared component that starts the car. It is possible for either component to fail exclusively of the other. The fact that your other key works, suggest that the radio frequency component chip is done for.

 

The Ir and

the Rf both open the doors. Thus the Ir receiver in the door handle.
Radio frequency does not need a little red plastic window to transmit its high frequency short distance waves into

If you clean the battery contacts make sure not to touch them or the battery contact points with bare hands.
Also you might try inserting the key in the ignition and let it sit there for a bit to resynchronize the unlock/lock function per factory protocol.

 

Thanks for the suggestions.
This is what I have found. The red light flashes strong on the remote that works and very weak on the bad remote. If I switch the battery holder between remotes, then the good remote still works and has a strong red flashing light, regardless of which battery holder is in it. So the problem does not seem to be with the batteries or the battery holder but with the rest of the key.

But after switching the battery holders between the 2 keys a few times, now both remotes work and light up strong. So there may be an intermittent contact issue.

Anyway both keys are working at this time. I hope they stay working.

Paul

 

Just for the protocol - I remember that you can start the engine without batteries in the key, because it's powered by the car (induction). So there is a way to open your car even if you don't have batteries - just pull out the mechanical key, open the drivers door with it (the alarm turns on), quickly go into the car and insert the smart key (the alarm goes off). Unfortunately, you can't engage the alarm without batteries.

 

i have a 2003 mercedes S500, today i tried unlocking my door with my key fob, but never worked. i used the metalic key to open door, when i put the fob key into ignition , it didn't work . the fob light never lit up, when pressing on its buttons . the front console system was working. even though the batteries where fairly new, i changed them to brand new batteries , and again fob key didn't work and red light never turned on. also, last time i used key fob was 2 days ego , and there was a huge rain storm here in new york , maybe it got wet, there is a small hole in the fob key casing, but its been there for a long time, with no issues . what can i do ???

 

Did you ever get it fixed? I have the exact same problem now. ?

 

replaced batteries used to be able to unlockd and lock doors with foy pocket can sti unktrunk any advise

 

Huh?

 

you are in the W210 site, and this really applies to the W210/W208...

Their are two systems here RF(radio frequency) and infraRed(like your TV) built into the car. The RF is the one doing most of the work, and generally when it fails radio reception/selectivity falls off too, and my understanding when this fails this module is about $1000 and coded to your car it is under the deck-lid on the left on left-hand driven cars. Now, you could have corrosion problems from the roof antenna to this module, but do a continuity test to see if the antenna cable is not open from module to the antenna...

Hope it helps,

Martin

 

The remote key for my 2002 E320 stopped working too. I went to the dealer and had to speak with a service advisor. He said it would be $250 to replace the key. That night I went home and after I washed my car I decided to just put the metal key in the door lock and turn it a couple times and then press the button on my remote. The remote actually starting working again! I don't know if this is just coincidence but maybe there is some type of cycle you have to reset or something. Anyway it is working fine now.

 

1998 c280. I still can't get the car started and am not getting any signal from the key remote with new batteries. Has anybody had a problem similar to this? Will a valet key work to start the car?

 

Your valet key should work (if the problem is with your key but not the EIS (Electronic ignition switch).

I assume the door lock / unlock part (non- infra red by radio frequency) part works ? Do you see the light on the key flashing when you press any key on the remote ?

It is probably a broken connection from the pick up coil to one of the posts or track on the printed circuit board. If so you can get it repaired if you do not have very good soldering skills.

 

Does the key electronics look like this ?

 

Its similar but its a different shape. Its a rectangular shape. It is almost identical to the chip linked in this youtube video.

I just took the key and chip to the local key shop and they managed to fix the infrared reading so the button is working now. The battery is not connecting well with the chip so it was only intermittently working.

They also told me that I was missing the transponder (RF?) and described it to me and I believe it flew out when I opened up the key to put new batteries. Do you know what the transponder is supposed to look like and where its supposed to go inside the key fob? They told me its a black rectangular piece and I believe I have that but its not attached to anything so not sure where it is supposed to go. My car is about 30 miles away from me and I am about to head out and try the key with the transponder

 

They also told me that the key is required to have this transponder very near by when the car is starting or it won't start as a security feature.

 

Yes, you can temporarily tape the RFID chip near the infrared light and try to start the car.

 

please help

I have a 2003 e320 and yesterday i turned my key to the position right before you turn on the engine, and i turned the key but really quickly and let go, the car didnt turn on but my instrument cluster was acting up, my turn signal didnt work, my front head lights dindt turn on and when i was driving, the rpm gauge was not working, so was my km gauge, and the most worrying thing is that my fan in front of the engine is constantly running at high speed for no reason, if you have any suggestions please contact me at this email donaldkokojumbo@gmail.com

 

I have a 2003 e320 and yesterday i turned my key to the position right before you turn on the engine, and i turned the key but really quickly and let go, the car didnt turn on but my instrument cluster was acting up, my turn signal didnt work, my front head lights dindt turn on and when i was driving, the rpm gauge was not working, so was my km gauge, and the most worrying thing is that my fan in front of the engine is constantly running at high speed for no reason, if you have any suggestions please contact me at this email donaldkokojumbo@gmail.com

Not very clear. You say your car did not start, then you say "when you were driving" . Does your car start or not ? If your fan is running constantly, you need to disconnect the battery, wait 10 to 15 minutes, reconnect (with the key out of the ignition) and see if the fan is still running.

Do you know if your battery is in good condition ?

 

It should go into somewhere close to the infra-red lens side. Yours is not the same as mine, so it appears that it relies on the RFID chip (small rectangular black piece) to start the car. The infrared part is just to lock unlock. There should be a slot in one of the casings that it drops in.

 

Ok so yes the car runs but the instrument clusters dont work like i cant see the speed im doing(and when i rev the engine the rpm gauge is not moving, the turn signals dont work and my headlights wont turn on. I also notice that the fan in front of the engine is running at full speed constantly(which it never did before). Today i noticed that when i turn the ignition faster like instead of turning the key and holding it until the car starts, i just hold(turn the key) for a quick second and let go , then the car works just fine, the signal and speedometer with the rpm is working, and the fan doesnt run at high speed.I think there might be a problem with my ecu or like an electronic component because when i bought the car, i used to hold the ignition longer and it had no problem. If you think you know what the problem is please comment, it helps and thanks for the advice.

 

Ok so yes the car runs but the instrument clusters dont work like i cant see the speed im doing(and when i rev the engine the rpm gauge is not moving, the turn signals dont work and my headlights wont turn on. I also notice that the fan in front of the engine is running at full speed constantly(which it never did before). Today i noticed that when i turn the ignition faster like instead of turning the key and holding it until the car starts, i just hold(turn the key) for a quick second and let go , then the car works just fine, the signal and speedometer with the rpm is working, and the fan doesnt run at high speed.I think there might be a problem with my ecu or like an electronic component because when i bought the car, i used to hold the ignition longer and it had no problem. If you think you know what the problem is please comment, it helps and thanks for the advice. Mrboca

 

Just an update. The car now starts and works thankfully! When I took the key apart, the RFID chip (transponder) needed to start the car flew out of my key. I found that part and inserted it back in my remote key and the car started. Without that RFID chip, the car won't start as a security measure so keep that thing secure and be careful with it because I don't think there is any way to get a new one if it is damaged or lost. You probably have to buy a new key. I am not sure about that last sentence (actually would be interested to know if you are able to get a new RFID chip if needed) but from everything I have read its hard to replace damaged Mercedes keys.

Luckily I was able to resolve this situation. Thanks MrBoca for the help and guiding me along. I feel like people don't talk about the RFID piece very often. It is one of the first things people should look for when they can't start the car due to key issues. When taking a key apart, always check and double check that you know where the RFID is at all times. I don't think you can get a new one.

 

:thumbsup::thumbsup:

I am glad you solved your key problem. With RFID based security, your car's ignition authorization system is much less complicated than the subsequent generation keys with no metal ignition blades and with more sophisticated electronics. My other cars have keys with the RFID chips in them, and never had any trouble with them.

 

Hello All, my w210 remote key wouldn't open the car from 15 meters so i thought the batteries were weak and just replaced it. Upon replacing the batteries, the remote key wont open or close the doors :-(.
The car starts without any issues however. I just locked the car with the metal key once. Later i opened the car with the metal key and then the opened the other doors using the switch in the dashboard.
Now the other doors wont close when i try to lock the car with the metal key. The remote is not working and am not able to lock the car and i had to manually close each door and finally lock the car using the metal keys.
The red light on the remote key does not flash.
Does this sound like an expensive problem since when i called the dealer, they just told to replace the entire key unit at a cost of $4000.
Any advise will be helpful.
Thanks

 

Test your Infrared transmitter of the keyfob to make sure you have blinking sender when you press lock/unlock button, and the infrared tip is viewed by a smartphone camera. If not working, the remote has no proper power or defective. If you see the flashing IR light at the camera, try locking and unlocking with the IR function (hold it close to the door handles). After you changed the battery the keyfob may have lost its synchronization that needs to be resynch.

Does the central locking / unlocking still work to lock and unlock the car ? You may have a problem with one of the door close switches. Does your trunk lid open with the remote or interior switch ?

 

Thank you mrboca for your quick response. I will check the key tonight and see if i have the infrared through my phone camera. The central locking was working just fine, However i opened all the doors to put in some stuff and when i tried to close the doors with the metal key, the central locking did not work. I had to shut each of the doors manually. Also i have not attempted to open the boot. I will have it checked tonight.

 

I just checked the keys and found the infrared light does not flash when i checked under the camera.
Any ideas?

 

Probably a bad install for the battery or some connection broke when you installed the battery.

To check the remote battery, press and hold the transmit button for more than 1 second. If the battery is good you should be able see a red light flash on the remote. If not, open the remote and check the installation, broken wires / tracks.

To re-synchronize your remote, point the remote at the rearview mirror and press the transmit button twice. And in 30 seconds insert the attached blade key in the ignition and turn the key to the second position.

 

Just going to add my recent experience.

One of our key fobs developed a problem. It would open doors and trunk, but would not lock doors.

I took it apart and noticed that the microswitch under the lock button had broken off the circuit board.

I sent it to a guy in Toronto area and he repaired unit. Cost me $100, but that included a new casing because old one' buttons were kind of deformed.

Just be careful when using fingernails or whatever to try and make doors open or lock. The little switches under the casing buttons are quite fragile. Treat them with care!