Anthony199

Hello,

I have a 2012 e350 sedan, and am having issues with unlocking the car. The unlock button on the key fob (I have only one, and it's not a keyless go remote) failed to unlock the car. This started happening all of a sudden today, but I was able to get it to unlock once or twice after noticing it stopped working. The trunk and lock buttons work, and I have changed the key fob battery today to see of this resolves anything. When the unlock button on the fob won't work, I use the key to manually unlock the car, and when I get the door to open, the unlock buttons from inside the car on the driver and passenger doors are also having trouble unlocking. So I would say the key fob is having the most trouble opening the car, then come the buttons on the door. I have no problem starting the car.

What should I investigate? Car battery, fuse in the trunk, lock actuator, etc...?

Edit: car not unlocking at all from remote. The red light turns on only after pressing the trunk or lock button and the car taking action.

Thanks

AkaSigFreak

Have you tried changing the remote battery?

Anthony199

Yes, I have. Didn't change anything.

konigstiger

Definitive diagnose, need to pull fault codes using MB diagnostics. DIY try replacing antenna amplifier (part # 2128201789) located in left c-pillar. You can start shopping here: https://www.ebay.com/itm/MERCEDES-E3...-/131997966192

Anthony199

So the key unlock button only stopped working now. I can't get it to unlock at all from the key fob. I might get it diagnosed at the dealership, but what does the antenna amplifier do? If it has failed, wouldn't it not respond to the key fob at all? I can still lock the car and open the trunk from the key fob, and can still use the buttons on the doors to lock/unlock the car.

konigstiger

Door unlocking is based on radio frequency, antenna amplifier receives RF from key to unlock doors - first DIY step to resolve. Not comfortable chasing problem and not under any warranty, have independent with MB DAS check it.

Anthony199

I found really cheap ones used online, I might give it a shot. Meanwhile I'll get it to an Indy to get it checked out.
This antenna, you mentioned it's in the driver side c-pillar. Do I need special tools or can I just remove the liner and replace it? For some reason, I thought it'd be under the antenna fin on the roof.

konigstiger

Remove liner, plug & play.

LeoJo

if u fixed already. how did u do?

Anthony199

My key fob was bad. $400 at the dealership, $250 from the service center at the dealership directly (lol). Took a few hours and got a new key.

BenzV12

Good to see it was fixed for good

LeoJo

ive replaced antenna fuse(#26 7.5A) but there is no changed.
so i decide following this youtube.


- i only can lock/unlock with Fob beside of driver's door keyless entry button. (have 2 original keys. all new batteries) (only 1feet distance)
- 1ft distance, all remote fob functionsare ok.

ill update here after.

Left Coast Geek

um, there's no IR sensors, at least not on the US model 212's. I believe they use both high frequency and low power low frequency RF, one to detect the key is inside/outside the car, and the other for the actual command and control signals. mine has the option where if the keyfob is on your person, you just touch the inside of the door handle to unlock, and when you get out of the car, you just touch the outside to lock, so you don't even 'use' the fob, it just has to be present.

LeoJo

my w212 e300 is philippines model. and fob was working well. but there is problem after some wiring problems.. . . . i need to do what i can do before spending a lot more. i already spent about 3000usd for 2monthes😂🥲