Originally Posted by jay_bob

This vehicle has the first generation DAS (Drive Authorization System). I've had experience with this when I had my E300.

Do you have the all black plastic key (panic button in the rear end) or a replacement (with chrome sides and the panic button on the piece that inserts into the dash)?

The on board diagnostics does keep track of what is holding it out from starting, but this requires the dealer level Xentry system to properly diagnose.

Several forum members (including myself) have clones of the system for diagnosis. If you edit your profile and put where you're located it will help other members know where you are.

One thing to be careful of is that the dealer will happily sell you a new key for around $400, matched to your VIN. The problem is that you have the first generation system and the latest type chrome keys (that were in use up through about 2016 or so) are not compatible with the first generation system.

If you just bought the car and the key is football shaped with chrome sides the seller may have gotten a replacement key from the dealer before selling it. The problem is that the new keys only work intermittently in my experience.

When I had this problem the dealer said they could replace the electronics in the dash but it would cost more than the car is worth.

But there is another option, there are locksmiths out there who specialize in these computer chip keys. They have a tool that pulls the security codes off the chip in the ignition switch (take out the switch module, disassemble the module, unsolder the security chip and put it in a reader to get the codes, then put it all back together) and use that data to make replacement keys (using NOS or surplus old style keys).