Key won't turn in ignition

[tymead]

Please forgive me if I ramble, but I'm new to this forum. I have a serious problem and am desperately seeking answers. I have an 2003 S430. I parked the car a couple of days ago, and now the SmartKey works occassionally and when I put the key in the ignition, occasionally nothing happens. Bottom line is sometimes everything works and at other times nothing works.

So, I ordered a new key, got home and put the new key in the ignition and the car started. In fact, I tried the old key and it worked also. A few hours later, I tried again with both keys and neither of them worked. Now, one more thing. When the key worked, I locked the doors. I had to use the valet key to unlock the door. The alarm goes off, of course; then I put the key in the ignition, and guess what -- the car starts. But not for long.

I did get a malfunction message. I believe it was something like "presafe
failed." I can't get back to the message because the keys don't work.

Does anyone have any ideas on ths one?

[compress ignite]

Technologically crippled as I am,all that newfangled Electro/Laser/Low Frequency types of communication between the Key and the Automobile is
VooDoo to me.
However,Most of the East Coast Techs (Arthur Dalton,Stevebfl,...)keep early hours.One of the Electronic Wizards will be along shortly after first light I'll bet.

Are you saying (As your "Header" states) that the key ,when inserted in the
Ignition Switch Tumbler will not turn to the "Run" or "Start" positions?
In the older models (70s,80s,90s) Ignition key that will not turn is First Warning
(And maybe the Last)that the Ignition Tumbler is "Going South"on you.
[Ignition Keys are Steel...The wear takes place in the Tumbler.]

[stevebfl]

I can't imagine doing any meaningful diagnostics here without MBs diagnostic computer. Other than verifying the powers and grounds to EIS, there is really very little esle available and even throwing parts at it will require the computer to finish coding.