Hello everyone,

I have a 2003 clk55 and it DOES NOT have keyless go. I've been having some issues with the keyless entry not working. When I first got the car it worked fine from 50 feet, then it slowly stopped working to the point where I needed stand right next to the door and it would work. Now it doesn't work at all.

I purchased a new key FOB and put a new battery in the old key. I've cleaned the infrared sensors on both of the doors and both keys with alcohol. I've checked all of the fuses in the entire car.

The car is tinted in the rear window, and it does have aftermarket stereo. The keyless issues started months after these modifications were made.

It seems like the RF signals are not being recieved by the car at all. It also looks like the infared was working for a while when I would stand right next to the door to unlock/lock the car. But now both aren't working. The car starts fine so I know the ignition infrared sensor is working fine and the keys are sending out an infrared signal.

From my research, it seems like it could be an antenna(where are they located?), or the COM bar. Anyone have any experience doing this yourself or troubleshooting the issue? I am mechanically inclined and have no problem changing the parts myself, but I don't know if I need dealer tools for programming.

Any input would be appreciated.

 

Assuming you have a coupe and not a cabriolet, there is an antenna amp located on the rear glass, under the stubby antenna. It controls all the RF communications fro the vehicle, including RCL (remote control locking), FM radio, satellite radio, and Cellular.GPS for TeleAid. First, check fuse #8 (on the rear SAM, in the left side of the trunk). If it's blown, that's likely your problem. If not, then it could be either a bad antenna amp (they are a problem on the W203, not so much on the W209, but not unheard of). Also, I'd be suspect about the tinting. The antenna amp is attached to the glass where is makes contact with the antenna system in and on the glass. It's common for it to be damaged when tint is applied - if the tint guy pushed on it, it can come unglued from the glass and fail to make contact with the wiring. Unfortunately, the only way to fix that is to replace the glass wit the amp module pre-attached at the factory.

 

I had similar symptoms and replacing the auxiliary battery was the fix for me. The keyless go system and central locking system run off of this hidden battery.

Best wishes for finding a quick and cheap solution.

 

There is no auxiliary battery in the W209 liek the W207. This extra battery is only used on cars with the electronic shift lever so that they can be shifted in and out of park if the main battery dies.

 

Mine has been really weird that keyless entry is spotty for the driver door but trunk and passenger door work 100% of the time. :S