Both of my smart keys worked to start the car but didn't work to unlock the car. I tried new batteries, but that did not work. I bought a new key and it does not work to unlock or lock the car either, but does start the car. The central locking system works fine as does the automatic locking system. I have been told that the problem is either with the antenna amp, a control module or a central system. Is there a way to know what the problem is without doing a trial and error dance? I was also told that there is no way to hook the car to a computer diagnostic system. Is that correct?

 

If it is a W203 as from your profile, it could be the antenna amplifier contacts to the rear window antenna wiring. You could try to push the roof lining up at the rear where the amplifier is.

Did you try the IR option, point with your key tip towards the door handle IR receiver from decent distance. This should operate door locks even if the antenna (amp) is faulty.

Of course every modern car can be diagnosed with diagnosis tools. In this case you might not find a lot of info though, possibly just that the car does not receive the message from the key.

Welcome to the forum.

 

Thank you Diesel Benz. I tried the new key pointing it directly at the lock and the doors locked and unlocked as they are suppose to. Does that mean that there is still a problem with the antenna amp? If so, and I don't repair the antenna amp, might I have any other problems as a result of a faulty antenna amp? The radio seems to be working properly.

 

I have 2007 clk 350 conv. I have to hold the smart key within a 1/2 inch of the door handle and only works on passenger side then only after many tries, stood in parking lot at dr.office for about 30 min. also radio cant find stations, except when at top of tall bridge then only for a second, HELP ????