Unfortunately once all eight keys have been used you have to replace some pretty expensive parts. Personally, I think it's a lousy deal but there's no way around it. I'll try to keep the explanation simple. The AAM is the control module that, among other things, verifies that the correct key/transponder is being used to start the vehicle. It does this by reading the chip which is embedded in the transponder. If you look at the ignition switch you'll notice a plastic ring around the key hole. This appears to be ornamental but it actually gets powered up by the AAM when the key is switched on. The chip in the key is turned on inductively and sends a coded message to the AAM. The AAM verifies that it's the correct key and sends another signal to the ME-SFI control module. ME-SFI controls engine mangement. Once ME receives the start authorization signal from the AAM it sends the appropriate signals back to the AAM to energize the fuel pump and starter relays. As you can see, MB made it pretty difficult to defeat this system.


Now, here's where it gets confusing. When an AAM is replaced, the dealer receives a "dumb" one. In other words it won't work until it's been learned to the vehicle. The way it's learned to the vehicle is simple. The AAM also includes a "workshop" or "single use" key. This is just a regular blade key, not a remote key like you already have. This key has a chip embedded in it as well, but this chip contains ALL the vehicle information for all eight keys assigned to the vehicle. When this key is put in the ignition switch and turned on, the AAM reads all the information from the chip and will now work with any key assigned to that vehicle. The problem here is that when all eight keys have been used, MB will not supply a "workshop" key identical to the original keys. The entire vehicle lock set must be replaced. This is around $500.00 if I remember correctly. The AAM and ME-SFI control modules also have to be replaced. This is why it's so costly.


I sympathize with your predicament but please don't beat up your dealer. They can't do anything about it. I've been in this situation before and believe me when I tell you that I didn't enjoy taking $2000.00 from a client who only owned their ML for about two months.


The only words of caution I can give you are to have your dealer make sure the problem isn't something as simple as the DAS ring around the ignition switch or the immobilizer, which the ring connects to. These parts are inexpensive and can cause the symptoms you describe. I'm actually suspicious because you say that both keys stopped working at the same time. Something tells me that your keys are OK. Let us know what happens.