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Q: 2001 Mercedes S500 stuck in antitheft mode

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Locked key I trunk. While retrieving it the alarm activated. Since then alarm won't arm or disarm and car won't start. It cranks but won't turn over. Windows work by the switch but nothing else responds. Had computer reset at European car repair shop.. even changed the EIS, ECM, key and shifter. Still same symptoms.

My car has 189000 miles.
My car has an automatic transmission.

Your car will need to be scanned by the Mercedes appropriate equipment like the SDS or the Baum tool. Not all independent shops go to the expense to equip themselves with such expensive stuff so you might end up having to see a dealer. If the car is actually in lockout, that is handled by the DAS (driver authorization system) and there will be codes there that can only be read with the right stuff. But I wouldn’t rule out some other problem, like a failure in the power distribution box. these cars are very complicated and it seems they rarely have just one problem at a time. To get a hands-on opinion, you can contact Your Mechanic. They can send a technician to your home or office to check out your Mercedes and let you know what it is going to take to solve your problem.

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