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Discussion Starter #1
Hi everyone,

My 2001 C320 does sometimes not recognize my key and I am unable to remotely unlock the doors and start the car. Most of the time, it works just fine but I had to call AAA 3 times already....only to cancel a tow when the key all of a sudden starts working again without a problem. When it DOES NOT work, there is no indication the car recognizes the key at all....no sounds, flashing, NOTHING. Just like you were clicking a key of a completely different car. Again, most of the time it does not work I will just wait 30 minutes or so and then it'll work again.

Any ideas and/or help with this is greatly appreciated!

Cheers,

David
 

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Do you have a spare key? If so does it exhibit the same symptoms? Check the battery (car battery) a weak battery will cause the ignition switch to not recognize the key(s). I've had a key stop working in my 202, sometimes they just wear out. Could be a worn out key, about $200 at the dealer for a new one. Finally it could be the electronic ignition itself, indy or dealer fix if so. The car will need to be reprogrammed. By your description it sounds like a weak battery. When the keys stop working they just STOP and seem to never work again.
 

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Discussion Starter #3
I do have a spare and it is indeed exhibiting the same problem....I have replaced the batteries of both keys as well. Also, the problem only arises when my car is NOT parked in my garage. Sometimes I park it outside my house or in an open parking structure at work and that's the only time this happens. It makes me think that it has something to do with humidity or cold (although I live in Socal where it never freezes). Also, sometimes the problem does not happen for weeks and then all of a sudden I can't unlock the car for 3 mornings in a row. Actually, for the last 3 days (car parked outside every time) I could not unlock the car, would then take my wife's Benz and she will always call me later in the day saying that she was able to unlock the car w/out a problem.

Thank you very much for your response!

Cheers

David
 

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CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
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So the key won't turn the ignition switch either? Or is it that you can't unlock the doors so you can't get to the ignition swith?
 

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Discussion Starter #5
@rudeney: I cannot turn the ignition at all when this happens. The only way I can open the car doors is by using the little "physical" key inside the remote key. Of course the alarm will go off when I do that...which is obviously irritating.
 

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OK, just making sure and eliminating the obvious. It is possible this is a problem with the vehicle battery. If it's more than three years old, I'd definitely have it checked (remember, you can call MB Roadside and they can check it and even replace it for no labor - just the price if the battery, about $160).

The deal is, there is no real connection between remote locking (RCL) and drive authorization (DAS). RCL uses the battery in the fob to transmit it's signals and it's a different vehicle system that validates that RF signal that what validates a key to start the engine. DAS uses an RFID tup antenna in the ignition switch to power the part of the fob that activates it's infrared transmitter, then it communicates with the ECM to validate the key for starting. Other than some things like the CAN bus itself, there is not anything besides the vehicle battery that is shared between DAS and RCL.
 

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key wont work in cold weather

Hi krass,
any luck with the key issue? my 2001 c320 is doing the same thing. the colder it gets, the longer i have to keep pressing the unlock button. it's 24 degrees now and it wont open at all. same thing, new batteries in remote, etc. once it does unlock, it works great until it sits out overnight (or in this case, 3 or 4 hours).
 

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Discussion Starter #8
No, unfortunately I haven't figured out the underlying issue with the locks/keys. I've been keeping my car in the garage so my car has been unlocking/locking fine. I'm planning on taking the car in sometime and have it looked at. I will post the outcome here. Thanks for your reply and let me know if you find out anything.
 

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thanks

I will, thanks so much for the reply. I've got two emails in to the local dealers as well and will hopefully know more soon. I'm wondering if perhaps it could be a bad relay or something.

This morning it took a half hour of pressing the unlock button when it finally opened. But after that all was good - It's as if a cold, faulty relay kept trying to operate the alarm until it heated up. I'm trying to locate the unit, hoping it's inside the car so I can bring a portable heater out there.

I'll let you know what becomes of it..B
 

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Discussion Starter #10
B, I've noticed that whenever I fail to unlock the car and walk away from it for a few minutes, when I get back it usually opens. I'm in southern CA conditions and it never gets below freezing so my problem may be less severe here? Have you tried to use your spare key when you fail to unlock? It does not solve the problem for me.
 

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Key won't unlock in cold weather

I have a 2001 C320 which is not unlocking now that it is cold. I replaced the batteries in both keys and reprogrammed them, replaced the car battery and it still won't unlock. Once the car is warmed up it works fine. Huge pain. Does anyone have a solution?
 

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Discussion Starter #12
Seems like we're having the same problem but unfortunately I don't have an answer for the underlying issue yet. I will definitely post any help when I get it...please do the same.
 

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Discussion Starter #13
problem persists....

did anyone ever find a fix for this problem? My locking problem has gotten worse and now I haven't been able to unlock/drive my car for the past two days.
 

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This is likely a problem with the antenna amp. It's attached to the back glass, under the stubby antenna. It's a common point of failure on the W203.
 

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I had a similar problem with my 2007 C230, all of a sudden one day the smart key would not lock or unlock the car but the car would start. I changed the batteries in both keys and the same result. After about a half hour I opened and shut the trunk after getting something out and presto, no more locking or unlocking issues! I am certain there is no real correlation here but I have not had any trouble since—knock on wood!
 

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If they key starts the car just fine, but wont work for Remote Control Locking, then it's either (1) a weak or bad battery in the key or (2) a bad key or (3) a problem with the antenna amp under the rear glass. If they key also is not recognized by the ignition switch, then first try another key. If that works, then you have a dead key which will need to be replaced. If the other key doesn't work either, then it coudl be a problem with the vehicle battery, or the vehicle's security system (DAS/EZS).
 

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Cold Weather Key Issue

Hi Guys...
I had an issue where my car would not unlock anytime it was cold in the evenings. Sometimes it would take a few clicks, but as it got colder, it could take a few hours and sometimes it just would not unlock, start, etc. after an exhaustive forum research with no results, I contacted my local Mercedes Benz dealer in Lynwood, WA and spoke with Garrett. He told me that it was most likely the EIS and they had seen this before. Sure enough that was it. It was not the battery, remotes, or anything of the sort. It was the EIS and I spent about $900.00 to get it replaced (it has to be coded, keyed, etc.). Everything is perfect now, but the expense was painful. However, not nearly as painful as waiting for my car to open in the morning. If your car has other issues other than not responding to the remote, it could be something else. BUt basically, if the remote wont open it or the ignition wont recognize the key, this is it! They are great cars which is why we drive them...but sometimes we have to bite the bullet. Good luck...B
 

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My 01 c320 has the same frigging prob. But with mine if it doesnt recognize the fob, i take it out and turn it around and it starts. go figure
 

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Hey guys, I have a similar problem. My W202 will not unlock when its cold outside, but this does not happen all the time. When it does, I point the key from a short distance at the IR (infrared) window located on the front door handle. Sometimes I have to use the passenger door IR. For me, this always works. Make sure the IR receiver window on the door handle is clean.

An explanation is in order. The smart key uses two transmitters: RF (radio frequency) and IR (infrared). RF works with the antenna amplifier, and that's where the problem lies. These things break all the time. IR is short distance, and does not use the antenna amp.
 

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Discussion Starter #20
EIS ignition switch was the problem.

To bring this tread to a close from my end, the problem was the EIS ignition switch. The ignition is one of the few problems an independent Mercedes mechanic cannot fix themselves as Mercedes does not sell the part to outsider.

Price point: Parts - $677.10
Labor - $524.88

My car was at Mercedes of Calabasas for a week.....

Hope this does not happy to any of you....
 
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