Repair And Fix it

Replace the battery in your SmartKey. Purchase a new battery at any auto parts store or any authorized Mercedes-Benz dealership. Open the SmartKey fob using a sharp object, such as a butter knife, and trade out the dead battery for the new battery. Test the SmartKey remote.

Repair a SmartKey that no longer starts your cars engine by turning off all of the non-essential functions in your car, such as lights, the radio and the heated seats, then try to start the ignition. Jump-start your car if this does not work and contact your Mercedes-Benz service department for a repair appointment.

Pull the door handle of your Mercedes and turn your SmartKey to the second position in the ignition. Use this method if you cannot lock or unlock your car with the remote.

Contact Mercedes-Benz. The Mercedes-Benz website allows you to enter your zip code to find the dealership nearest your location.

Explain that your key fob is not working correctly. Be as specific about the problem as you can. For example: tell the dealership if your key fob only works when you are unlocking your doors and not for anything else. The more specific you are, the better Mercedes can diagnose your fobs issue.

Attempt to fix your key fob if the mechanic at Mercedes tells you to try any self-diagnostics on the fob. Sometimes the mechanic recognizes the problem without ever seeing the fob, based on your description of the problem and will walk you through the repair process. If he or she cannot, youll need to take your key to Mercedes for repair.

Take your key to Mercedes if self-diagnostics you tried on your own and/or that the mechanic advised you to try do not work. From this point the process is up to Mercedes, such as how long you need to wait, whether or not your fob is fixable or youll need to order a new one and how much the repair/replacement will cost you.

Close all the doors on the vehicle, including the trunk and hood. Turn the ignition to position 1 and press the system selection button on the lower-left side of the steering wheel to cycle through the menu options until the kilometer reading and temperature values are displayed in the multifunction display.

Press and release the trip/reset button three times quickly; you should hear a chime sound and the voltage will appear in the multifunction display. Turn the ignition to position 2.

Press the scroll forward/back button on the upper-left side of the steering wheel; the service indicator should appear in the multifunction display. Press the trip/reset button one time; the oil type menu will appear in the multifunction display.

Select the oil grade for you engine by pressing the volume up/down steering wheel controls on the right side of the steering wheel. The engine oil grade for the 2003 Mercedes-Benz C240 is 5W-40 or 0W-40, depending upon your temperature climate; 0W-40 is recommended in colder climates.

Press the scroll forward/back button to confirm the oil type. Confirm oil reset, press R button for 3s will appear in the multifunction display.

Press and hold the trip/reset button for three seconds; the multifunction display will show a Service confirmed message. Press the upper scroll forward/back button until the service indicator appears on the multifunction display.

Press the upper system selected button on the lower-left side of the steering wheel until the kilometer reading and temperature values show on the multifunction display. Turn the ignition key to the 0 position.

Turn the engine off while your Mercedes is on a flat part of the ground and pop the hood of your Mercedes.

Locate the battery on the passenger side of your Mercedes engine compartment.

Loosen the bolt connecting the negative (black) cable connector to the battery using a ratchet. In order to eliminate the possibility of being shocked, always remove the negative cable connector prior to the positive cable connector. Upon loosening the bolt, the connector itself should pop off the top of the negative connection on top of the battery.

Loosen the bolt connecting the positive (red) cable connector to the battery using a ratchet. Pop the positive connector off the top of the battery.

Lift the battery out of its housing.