E320 car key doesn't work

I had the same problem with my 2001 E320. Roadside assistance came to my house and said it was a problem with the key. Ordered a new key (cost about $220 from Keys European in Van Nuys, CA) and the key worked. When I went to dealer to pick up the key, I spoke to a service consultant and he said that hes seen that problem before and replacing the key wont do anything (even though it did work). He said something about a ESI (something like that) and said that parts only on that cost about $600. So first thing you should try is replacing your key. Hope I helped.

Try both of your keys in the ignition, if neither turn, then it is likely the EIS Key Switch. The part cost for the switch is $480, vs. the cost of a key is $210. The labor to replace the switch is typically $260 from a Mercedes Benz dealer. I had my key and switch replaced almost 2 years ago. The key still looks like new, however the replacment key has already failed. It isn't the batteries, as the internal batteries power the remote locking only. The EIS switch energizes the chip in the key. My "new" key will not turn now, but my old "original" key still works. So, I know the switch hasn't failed again. Now to see if Mercedes will warranty the replacement key! Another tip with the key is if you hold it by the door lock and unlock it if you hold the unlock down, it will start to lower the windows to cool the car in the summer before you enter. If upon exiting, you hold the lock down, the windows will all close.

It's a smart key with a chip inside, the doors open by the conventional mechanical control of the key. The keyswitch for the engine "looks" at the computer chip and makes sure no one with a sophisticated key machine that could copy your key ... will be able to start your car ... unfortunately this means when the chip in the key or circuitry in the ignition switch fail ... you can't start it either ;~(.

You might need a new key. I had the same problem on 04/16/09 with my key to my 2001 E320. I called roadside assistance who told me that it was the battery, until he realized the doors and lights were operable. Then he thought maybe the steering wheel was lock (tell me something I didn't know myself), so I dismissed him; called Mercedes dealer whom stated that I should bring the car into the shop. Then I called husband, who stated that it could be the key. Husband came home, stuck his key into the ignition and car started up immediately. So, if you have a spare key, you may want to try to start the engine with that key. Good Luck!!!!

Lisa

I have the same problem and one key worked OK and the other on just unlocked the doors and trunk but would not turn in the ignition. I got a key fob from a junk yard and took out the induction coil and infrared diodes from the one in the junk yard and soldiered them in my inoperable key fob, and it worked fine. I believe that the problem is the diodes burning out on these fobs. You have to have a very fine tip soldering iron for this, its like soldering two fine hairs together! Does any one know where to get replacement diodes for the fobs? gadgetman&@comcast .net

Yes i had the same problem with my Bmw x5 the key that i had will open the door but will not start the engine but when i used the spare key it worked . it is something to do with the chip in your key you have to get a special device to solve the problem .

does anybody know the name of the computer or devise ?

Call Mercedes ask them. I think is the key. you may need to have a new key made.