Help with my door?
 

Hi, I have a 2011 E350 and the driver's door wont lock via the key fob or the central locking button. The keyfob DOES unlock, opens trunk and panic works. If I use the central locking on the driver's door before I get out all 3 other doors will lock except the driver's door. I must use the little key inside the keyfob to manually lock the driver's door from outside. Once again, when I press lock on the keyfob, I get nothing. The battery is new and I do not have a spare key sadly. Any help would be appreciated. I been tossing idea of buying the MB II scanner because I live in rural area.

A scantool is always a good idea.
My guess is that the driver door lock solenoid itself may have an issue, since everything else seems to work normally. I've seen on other vehicles where they can function in one direction but not the other due to weakening solenoid.
There's always possibility that something may be interfering with the lock rod but either way you would need to remove door panel to verify.

When I put the car in drive and drive off the drivers door does lock by itself.

Do you have keyless go?

No, there is no Keyless Go. I wish I had it.

Hmm, not being able to lock the driver door with keyless go is consistent with the car thinking the key is still in the cabin. But that's not the case for you.

To rule out the keyfob, maybe try a little experiment using the convenience closing feature (page 93 of manual). Leave the driver window down, exit the car and lock from outside with manual key so all doors are locked, then aim the keyfob at the driver door handle and press and hold in the lock button. If the car responds to the keyfob, then the window will close and the issue is likely in the door lock mechanism as Mud suggested.

I did as suggested, left drivers window down, locked door manually from outside, pointed keyfob and held lock and nothing. Tried it 3 times and nothing. My guess is bad keyfob lock button? As I mentioned earlier if I put car and drive off after like 5 mph all 4 doors will automatically lock including driver's door.

Yeah, it could be a bad contact under the lock button. My keyfob might be different than yours but there is a red diode just above the lock button. That diode should light up with each press. If it lights when you hit unlock but not lock, then I would think the keyfob is the issue.

Another thing to check in the car, when you get in car and close driver door (still unlocked not driving yet), are you able to lock the driver door using central locking button on door? If so, then I'd rule out the door and focus just on the key.

Ok. So I did some experimenting yesterday. I turned on my infra red and I could see that all the buttons on my keyfob transmit a IR signal EXCEPT the lock button!! So my guess is this keyfob isn't a 100%. Im kinda dreading this bc I know that dealer will prob charge me 600 bucks for a key.

Key piece of info.
Interestingly I just fixed what seemed to be lazy or intermittent remote operation on our Silverado. Turned out the contactors for lock and unlock on the fob rubber buttons were a bit worn. I bought a new keyfob and swapped out the rubber button pad into our original keyfob as I didn't want to have to go to dealer to program new fob. Works great now.
I took the long way around mentioning this as it could be that the contractors in your keyfob may be dirty or a bit worn as well. Could be that a look inside may yield a fix. But if I recall you said you had only the one key for the car. IMO never a good idea, I suggest that you do get a second key. Speaking as someone who seems to misplace things sometimes....

Agree it could be a mechanical issue, but maybe save tearing apart the key until you get the new key. There are so many one-key sales these days and they keep popping up on here. I can only comment that the reason for this is because the other key WAS LOST. That should give buyers pause and demand that two keys are provided when purchasing any car.

I called Mercedes dealer in knoxville and they quoted 270 total. Not as bad as I thought. Im gonna get an extra just for piece of mind anyways. Thank you Fisch, Mud and Key for your help!

Glad it worked out for you. At least you'll have the original to keep as a spare that does everything except lock. I would be tempted to open it up as Mud suggests but

I wonder if one of those $125 of $250 service coupons could be used for this. One just expired on 9/30. Hopefully there will be another in December or January but that a long time to wait.