HC-06 Bluetooth module not responding to any AT commands
The default baud rate is 9600, 8 bit, no parity no flow control (9600,8,N,1).
The HC-06 works with 3,3V ... You can connect the HC-06-TX (output) direct to PC-RX (TTL) but the PC-TX (TTL) CAN NOT BE DIRECTLY CONNECTED to HC-06-RX (input), due to 5V, then you have to put a level converter. In this case is enought to use a resistive voltage divider.

PC                 HC-06

RX &lt;-------------- TX

TX --&gt; divider --&gt; RX