my key will not turn in the ignition of my 2002 mercedes s430

If this started happening after you changed batteries in your key, then it is your batteries, they are the wrong thickness, try putting key in with out batteries in case, it should turn and start right up. I had the same issue with my 2002 S500 wrong thickness or batteries, after replacing batteries, they should slid right back into casing without forcing them in case. Because that will cause laser and/or key not to be read when stuck in ignition. You should hear a small electronic click when key is inserted, if not batteries are too bid and is pushing on key laser....I hope this helps....2002S500

Actually, when I could not turn the key it prompted me to change the batteries, U then bought a new FOB, still did not work. The dealer said that the EIS may not be reading the key anymore (rather old) so I have just ordered a new key and waiting for delivery. I was told if that is not it, it may be in the ignition. However, if the key does not work I'll take it to the shop. Thanks

Hi

I have the same issue with my W220.I slot the key in and couldn't turn. What should i do?

change the gas pedal.