Ordered a replacement master key (blade only, no remote included) for a '97 e420 from my MB dealer. The key opens the door okay but when I tried to start the car with this replacement key, the engine cranks and tries to start but stalls immediately. Then the green and red rearview mirror lock/unlock lights starts blinking.

I spoke to the MB dealer and was told it is the correct key and maybe I have to insert the new key several times in the ignition switch as the tumblers might have taken a set on the original key. I thought this was absurd but I tried it anyhow... it didn't work. I also asked if it was magnetically coded and if there is anything special about it and they said no.

Any ideas what could be the problem? Appreciate any help before I lose or break the only key I have left. Thanks!

The 1997 E420 has a DAS (drivers auth system). This system sends a signal to the key & must receive the correct info back from the key! EVERY key is numbered, and there is only 8 keys for the car! IF you lose a key & have to get a replacement key the dealer must know which key that is so that he can order the correct replacement. IF there is any question about this they should refer to SI MBNA 80/07 page 2. If they didn't specify any key they always will send key number 1.
YOU can check the key(s) number by removing the BATTERY cover

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M.B.DOC thanks for the info. I'll go to the MB dealer where I bought the key from and have them correct this problem. Although I just started going to this dealership (since I just got this car recently) I'm already a dissatisfied customer and will try to use another delearship if I have to.