Mercedes-Benz 2003 C 240 4MATIC Operator's Manual page 220

Controls in detail
Useful features
Operating the remote control
Turn key in starter switch to position 1
or 2.
Select and press the appropriate but-
ton to activate the remote controlled
device.
The integrated remote control trans-
mitter continues to send the signal as
long as the button is pressed – up
to 20 seconds.
220
Erasing the remote control memory
Turn key in starter switch to position 1
or 2.
Simultaneously hold down the left and
right side buttons for
approximately 20 seconds, or until the
indicator lamp blinks rapidly.
The codes of all three channels are
erased.
i
If you sell your vehicle, erase the codes
of all three channels.