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Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53149
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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I have a 2010 S550 My key recently went dead or something I

Customer Question

I have a 2010 S550 My key recently went dead or something I changed the batteries it still wouldn't work. Used mechanical key to enter car once I did the alarm went off and the car won't start. I think it is because I have been unable to get it out of theft mode. Any suggestions?
JA: Did you test the battery with a voltmeter? And have you ever changed one before?
Customer: In the key fob? Or the car? The car battery is very strong. It is the key fob that is a pr
JA: Are you fixing your S550 yourself? What have you tried so far?
Customer: I just changed batteries in key fob. I also tried resetting the car by disconnecting the car battery. But as soon as I opened door alarm went off again
JA: Anything else you want the mechanic to know before I connect you?
Customer: That's it. Tha
Submitted: 17 days ago.
Category: Mercedes
Expert:  Marty replied 17 days ago.

Hi, my name is***** sounds like a fault with the car battery, not with the key battery. I would see about getting the car jump started for this problem.

Let me know how you make out.

Customer: replied 17 days ago.
Will try it and see what happens
Expert:  Marty replied 17 days ago.

Please let me know how you make out.

Customer: replied 17 days ago.
That didn't work. The key is turning all the way to the on and off position but won't turn over or make any sound or click
Expert:  Marty replied 17 days ago.

Does everything else in the car work? Windows, radio, horn?

Customer: replied 17 days ago.
Nothing works. I can only lock doors while in car.
Expert:  Marty replied 17 days ago.

If the car battery is good I would have to suspect a fault with the electronic ignition switch. There is not much you can do yourself for this problem. At this point you need to get the car connected to a Mercedes tester to check the ignition switch and other modules in the vehicle for faults.

Customer: replied 17 days ago.
Ok thanks
Expert:  Marty replied 17 days ago.

You're quite welcome. One last thing you could try is a second key if you have one.

Please let me know how it turns out.

Customer: replied 17 days ago.
No second key. But I will definitely keep you posted
Expert:  Marty replied 16 days ago.

Okay

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