Please Help! Smart Key not unlocking/ locking door - Benzworld.org - Mercedes-Benz Discussion Forum

jma82 · 05-03-2008, 07:51 PM

I have a 2003 Mercedes Clk 320.. My smart key is not unlocking/locking the doors. But works when I put it in the ignition.

The day before I had my whole car tinted w/ Infrared Tint. So I thought it was that so I removed the film. but still the same problem so it cant be the film.

I have changed batteries on both remotes w/ mercedes certified batteries.
Both Smart keys including my spare does not work. So its probably not the key because both of them stopped working at the same time.

Can someone please give me some advice to what I can do???
Im trying to avoid paying big bucks bringing it into the dealer.

Thanks!!!!

**Musikmann** · 05-03-2008, 08:21 PM

The only comments I can make with confidence is that you have eliminated the most obvious possibility that the key batteries are bad. The other part of the picture is your key is a transmitter and the car has a receiver. IMO, this is where your problem resides.

unitfreebie · 05-03-2008, 09:35 PM

If you go now to the W211 Forum, there is a thread topic about Keyless GO about 13 or so topics down from the top.

Near the end of the thread is a link to a Keyless GO manual for the W211 which is pretty close to the W209.

If you read through the 41 pages, it will tell you that the CAR WILL TRANSMIT by RF (not IR) to the Keyless Go remotes from the doors, interior, and rear trunk antennas. However, the Keyless GO remote WILL TRANSMIT BACK to the car and be received by ONLY ONE antenna will is located in the rear window!

That tells me if the Keyless GO remote will not open any of the doors, trunk, or start the engine, then the rear window antenna is at fault. So did they apply any tint film on the rear window? If so, they probably cut the antenna wire when they cut the tint film to fit the frame. So look carefully around the top/bottom right side (on W211, maybe same for W209) of the rear window for the antenna wires.

That's my theory... anyone else want to take a guess????

**Musikmann** · 05-03-2008, 09:48 PM

You own practically the same car so your guess is probably better than mine. The only thing is that jma82 never mentioned having the Keyless Go option. Also he said that his key would start the engine, but would not lock/unlock the doors. I think you are correct in that it is the RF (radio frequency) system that is at fault because, if I understand it correctly, it is the IR (infrared) that enables the ignition.

unitfreebie · 05-03-2008, 10:11 PM

Oh.. minor point but you're right!

I wonder if the Smartkey antenna is also at the rear window, same as the Keyless GO???

I know both have the 315 MHz frequency, so I would suspect it be the same antenna on the rear window.

Say, wouldn't the Tint Man have cut the rear window heater wires too? So it the rear window defroster does not work, then the wires are cut for sure!

Hey! If you get the problem fixed.. Please let us know what was wrong!

jma82 · 05-04-2008, 10:50 PM

Hey Guys thanks for the response. I have changed the battery already (bought from the benz dealer) So it cant be that.
Also I do not have keyless go option on my car.
I have removed the tint on my back glass so it cant be the tint.
So by reading this thread infrared does not unlock/lock the doors its radio freq?
Does anyone have any other ideas?
I was also thinking the tinter might have cut or unplugged something so I looked under the top backglass from the backseat and everything looked fine.

jma82 · 05-04-2008, 11:08 PM

Also..I got the key working 1 out of a hundred times when I stand 2 feet away from the door sensor.
Does anyone know where the IR sensor and the Radio Frequency Sensors are located?
One dealer told be the IR Sensor is in the back glass and one dealer told me its behind the rearview mirror.

unitfreebie · 05-05-2008, 02:24 AM

I believe in the non keyless GO cars, the car's Radio Frequency receiver's antenna is located behind the front windshield's mirror and open/close ONLY the DOORS. But the Infra Red receiver is located only on the driver's side door handle (small dark red square window) and operates ONLY on the WINDSOWS/SUNROOF; and the limited to 5-10 feet with the key nose pointed directly at the IR window on the driver's side door handle (less range in bright sun light days).

The reason for the separate system is that Mercedes did not the owner to inadvertently open the window/sunroof as a safety/security factor; where as BMW and Lexus don't care as their system is RF and you can open/close windows/sunroof from 50 feet away from any angle.

Try going to the front of the car and aim the remote key nose towards the back of the mirror and see if it works better. The antenna in the remote key is located also in the nose of the key, it should be non-directional, but sometimes it works better when the nose is pointed at the mirror.

Good Luck!

jma82 · 05-06-2008, 12:32 PM

I pointed it to the fron behind the rearview mirror and it still doesnt work....
i looked behind the backglass to see if anything was cut or disconnected during the install of the tint. but everything looks fiine..
I checked all the fuses.
cleaned the sensor behind the rearview mirrow.
does anyone else have any suggestionS?

unitfreebie · 05-06-2008, 12:55 PM

Out of curiosity, does your rear window electric defroster work???

Does anyone who for sure where the antenna for the remote smartkey is located on the 2003 E320???

I believe it used to be located behind the rear view mirror in older cars, but maybe got moved to the rear window at the introduction of Keyless GO as they use the same 315 Mhz frequency.

Can anyone post the Smartkey technical manual here so we can figure this out?

Thanks...