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2000 Mercedes-Benz S500. Sold: 2000 C230K, Sold: 1997 Porsche 944S
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1,271 Posts
Discussion Starter · #1 ·
Strange. Weather dipped into the teens this past week.
Now my FOB Key will NOT Lock/Unlock the Door.

I have to use the little metal key to open the door.

The FOB Key DOES start the car, no problems, no reported
error codes.

Last night I put in a fresh pair of CR2025 Batteries.
Pulled the Mother board from inside the Key FOB, cleaned it up
reinstalled and still the same problem.

Guys, what gives here? :confused:
 

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2001 S500 Sport
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354 Posts
Could be the pse pump, does the soft close feature on your doors work?
 
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Deceased 05 S500. Current: Evo X MR , C43 AMG
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188 Posts
My car did the same. I did not diagnose it- simply replaced the keys and the problem was gone. Mind you it was held together with tape so it was about time.
 

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Outstanding Contributor
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1,963 Posts
To check if it is the PSE pump try the lock/unlock button on the dash, if it locks/unlocks the door then it is not the PSE pump.

Dean
 

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2000 Mercedes-Benz S500. Sold: 2000 C230K, Sold: 1997 Porsche 944S
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1,271 Posts
Discussion Starter · #5 ·
Everyone; my Dash Lock All Doors Button Does Work.
It also works automatically when I drive away/exceed 5mph.

It's daggone strange.
Doors open and close
Automatically close as needed
But the bloody FOB will not do what it's supposed to do! !

Using that little key is annoying.

At the very least, the ol' gal is driving, no problems.
So that's good!
 

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2005 SLK350, 91 300SL with Pano Top, 04 S500, 2015 Tesla Model S
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2,173 Posts
Do any other FOB functions work? Like the trunk opening or Panic?
 

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2000 Mercedes-Benz S500. Sold: 2000 C230K, Sold: 1997 Porsche 944S
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1,271 Posts
Discussion Starter · #7 ·
mrelbe;
Glad you mentioned it; in fact, the FOB Trunk Release and Red Panic DO NOT work.
Works within the car
But does not work on the FOB.

...that's strange, why you got something?
what are you thinking?


Charles
 

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S500 4Matic 2005, S550 4Matic 2013
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1,498 Posts
I would try the spare fob/key but I am afraid you might need a new one since something seems to be wrong within the fob itself. Good luck...
 

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2004 CLK 240 Coupe
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11,385 Posts
MB of F - Your remote key has 2 independent computer circuits inside. One could work OK while the other is faulty.

1) IR receiver circuit. Used to start the car by hand-shake communication via IR transmitter in the EIS. (ignition switch) This uses power in the car to energize the key IR circuits, so NO BATTERIES are required in the key to start the car.

2) RF transmitter circuit. Powered by the remote key batteries. This is for remote open/close the doors, trunk, etc. It communicates via RFantenna in the rear window, and the antenna amplifier.

Also (if you have the feature) there is a 'convenience' IR receiver by the front door handles that will open/close the doors & sunroof when used with the remote key at close range to the doors. If you have this, try the operation.

So (as the internal open/close door switch works) you could have: a) a faulty RF circuit in the key. b) faulty RF antenna/amplifier.

My money would be on the remote key RF transmitter circuit being faulty.
 

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W221 & Audio Moderator
2013 S550
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11,216 Posts

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2000 Mercedes-Benz S500. Sold: 2000 C230K, Sold: 1997 Porsche 944S
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1,271 Posts
Discussion Starter · #11 ·
Warren and everyone'
OK-I'm going to try and trouble shoot this, as per instructions above.

Daggone 20'sFahrenheit here and I am sick and tired of it.
 

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W209 CLK500 & W220 S430
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320 Posts
Just a simple question ?

I would try the spare fob/key
but I am afraid you might need a new one
since something seems to be wrong within the fob itself.

Good luck...
Could a new Mercedes Benz key fob be programmed to operate both of my cars ?
 

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W221 & Audio Moderator
2013 S550
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11,216 Posts
Since the keys must be matched to the Electronic Ignition System and the EIS*is matched to the particular car, I doubt it.
 
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