This problem is noticed on 2001 S340 Mercedes Benz.
Disconnecting and reconnecting battery never cause this problems.
If you car has security alarm system installed,then disconnecting and reconnecting battery will cause this problem.
In that case alarm needs to be reprogrammed.
But if you get any click noise or car turns over but not start,then this problem is not related to security alarm system.
In that case,there are few possibilities to be checked.
Did you jump started your car recently while this problem occurred.
If yes then this can cause the problem.
jump starting can cause the problem if done incorrectly.
Usually there will be an event that causes it. Usually it's caused by either an overvoltage situation from the alternator, reversing the polarity when jump starting or water intrusion into the modules.
The S class has some common problems with water entering the car through a plugged cowl drain. Check for water under the carpets and see if that might be attributing to the problem. This car has a complex electrical system. If there is no specialize Mercedes repair garage center near by then you might want to take it to someone who does.
How to troubleshoot car battery?
How to test starter solenoid?
http://schematicsdiagram.blogspot.com/2011/06/how-to-test-starter-solenoid.html
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How to test cars starter?
http://schematicsdiagram.blogspot.com/2011/06/how-to-test-cars-starter.html
How to replace starter in car?
car will turn over but will not start?
Car wont start?
http://howtobyme.blogspot.com/2011/10/car-wont-start.html
Disconnecting and reconnecting battery never cause this problems.
If you car has security alarm system installed,then disconnecting and reconnecting battery will cause this problem.
In that case alarm needs to be reprogrammed.
But if you get any click noise or car turns over but not start,then this problem is not related to security alarm system.
In that case,there are few possibilities to be checked.
Did you jump started your car recently while this problem occurred.
If yes then this can cause the problem.
jump starting can cause the problem if done incorrectly.
Or also its possible that battery terminals dirty or loose or not connected properly or battery itself is weak.
Test battery and starter for getting the issue confirmed.
See below the help solutions :-----
How to troubleshoot car battery?
-----------------
How to test starter solenoid?
http://schematicsdiagram.blogspot.com/2011/06/how-to-test-starter-solenoid.html
--------------------
How to test cars starter?
http://schematicsdiagram.blogspot.com/2011/06/how-to-test-cars-starter.html
How to replace starter in car?
-----------
car will turn over but will not start?
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