I have done all that on the ML320, remove negative terminal, remove the fuse, the radio and still says wait...... HELP !!

The only "reset" there is involves either leaving the negative battery terminal end off of the car battery a day or removing both terminal ends and holding them together for a minute. Proper procedure is remove negative first and install negative last. There could be a blown fuse in the back of the radio or more likely in a fuse box. But i would bet on the radio being junk.

You may have gotten lucky this time . That's a trick done in the 60's before transistors were used on vehicles an before PCM/ECM controlled charging systems . http://www.troubleshooters.com/dont_disconnect_battery.htm http://www.motor.com/magazinepdfs/042010_09.pdf If you don't know maybe you should take it to a ASE certified repair shop .

contact Mercedes as they will have the code on file

Car Radio Battery Constant 12v+ Wire: Red/White
Car Radio Accessory Switched 12v+ Wire: Black//Yellow
Car Radio Ground Wire: Brown
Car Radio Illumination Wire: N/A
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: Blue/White
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Green
Left Front Speaker Negative Wire (-): Brown/Green
Right Front Speaker Positive Wire (+): Black
Right Front Speaker Negative Wire (-): Brown/Black
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Pink
Left Rear Speaker Negative Wire (-): Brown/Pink
Right Rear Speaker Positive Wire (+): White
Right Rear Speaker Negative Wire (-): Brown/White

disconnect the battery terminals and then repeatedly depress the brake pedal 30-40 times in order to drain any remaining power from circuits. once this is done you may proceed with airbag removal.

Check for consumers staying on such as interior lights , radio etc.. To check for current draw, you need an AMP meter. remove the negative battery terminal. Connect one amp meter lead to the battery negative terminal and the other to the earth cable. Hold the cable against the battery negative cable, close all doors and press bonnet switch to closed position. Activate the alarm and wait for it to arm. Once it has armed itself, separate the earth cable from the battery terminal keeping the amp meter connected. read the current draw. Should be less then 100 milli amps. Usually +- 40ma. To check which circuit has current draw remove one fuse at a time and check if current draw drops. A drop in current draw will indicate that the problem is on that fuses circuit. Also check alternator charge rate. To check this hold a volt meter across the battery terminals. with engine off, should get battery voltage. Start the vehicle, battery voltage should rise to 13 -14v and maintain this voltage with the headlights on. The battery itself could be faulty, you would need to do a load test on the battery. Load tester needed to do this.

You can disconnect your negative battery terminal, wait five minutes or so, then reconnect it. This should clear the malfunction code. If, however, you have an anti-theft radio, make sure that you have the five digit code to reset it after disconnecting the battery. Disconnecting only one terminal might not effect the radio, but I wouldn't count on it.
If the malfunction code comes back after you disconnect the negative terminal, then something has gone wrong with your repairs.
Hope this helps you.

under hood fuse relay box
remove back up radio fuse for 10 second
if not remove negative battery terminal for 30 second

I've entered incorrect radio code and it is now stuck on WAIT. but i don`t have the code what can i do. pl. help me

leave the radio on for a few days, with the wait displaying, it will display CODE after a few days, 2 - 3 days, then enter the correct code , everytime u enter a wrong code the time increases.