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Michael Warfield
Michael Warfield, Factory Mercedes-Benz Technician
Category: Mercedes
Satisfied Customers: 3142
Experience:  Mercedes-Benz Master Certified technician
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2005 ML 350. Both key fobs stopped working. Replaced the

Customer Question

2005 ML 350. Both key fobs stopped working. Replaced the batteries and still not working.
JA: Have you checked the fob's battery?
Customer: Replaced batteries in both
JA: What is the model of your '05 Mercedes?
Customer: ML350 special edition
JA: Are you fixing your Special yourself? What have you tried so far?
Customer: I have replaced the batteries in both key fobs and they still do not work
JA: Anything else you want the mechanic to know before I connect you?
Customer: No
Submitted: 10 months ago.
Category: Mercedes
Expert:  Michael Warfield replied 10 months ago.

Hi, my name is ***** ***** am happy to assist you today! Thank you for being patient while you wait for your answer. If the lock button works on the dash but only the key fobs are inoperative, there must be an issue with the radio frequency coming out of the keys or the All Activity module that receives the signal and actuates the locks. I would first try relearning the key by putting it in the ignition, turning it on but keeping the engine off, then remove the key open the door and hold the "lock" button on the key while pressing unlock 5 times within 5 seconds. This procedure may or may not work. My next step would go to an autoparts store such as autozone (call first) that has a radio frequency key tester. It just checks to see if there is some kind of radio frequency coming out of the key. These ML keys unfortunately are very problematic and it is not uncommon to have 2 faulty keys. If the keys are actually working, then I would feel confident the All Activity Module (AAM) is faulty and will need to be replaced at european shop or dealer. Please let me know if you need any more information before you decide to rate me, thank you!