How do you change the refrigerant on a qx4?

To change the refrigerant in a Nissan QX4, first ensure the vehicle is off and the AC system is not pressurized. Connect a refrigerant recovery machine to the service ports to safely extract the old refrigerant. Once the system is evacuated, replace the receiver-drier if necessary, and then recharge the system with the appropriate type and amount of refrigerant, following manufacturer specifications. Finally, check for leaks and ensure the AC system operates correctly before finishing.