The Clg or CG code on Samsung Dryer Means: there's a clog somewhere in your vent system that needs to be cleared. This code should only come up in service mode. 

Check your dryer vent and make sure it's not stopped up. If it is that's the problem if not you will need to check the vent components inside the dryer itself for clogs. The video below shows how to change the belt on those model dryers. Once you get the front off you will see the lint filter housing, check it and check the vent inside the dryer for build up that would be blocking airflow. While your at it make sure the belt is in good shape and not broken and correctly attached.

If the venting and belt checks out then you will need to check the thermal fuse which is toward the back of the heater on the left side (See image below)

Check the fuse for continuity with an ohm/volt meter. If it does not have continuity it's bad and that is the problem. The fuse you need for that model is linked below:

If the fuse is ok then the thermistor sensor is bad and sending the wrong information about the temperature to the control. The sensor is linked below:

If none of the above fixes the problem then the main control board is bad. If you end up needing the part informaton for that let us know.

The video below shows how to replace the thermistor: