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Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53846
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: 7 months ago.
Category: Mercedes
Expert:  Marty replied 7 months 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 7 months ago.
Will try it and see what happens
Expert:  Marty replied 7 months ago.

Please let me know how you make out.

Customer: replied 7 months 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 7 months ago.

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

Customer: replied 7 months ago.
Nothing works. I can only lock doors while in car.
Expert:  Marty replied 7 months 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 7 months ago.
Ok thanks
Expert:  Marty replied 7 months 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 7 months ago.
No second key. But I will definitely keep you posted
Expert:  Marty replied 7 months ago.

Okay