When you establish connection between two Bluetooth devices, you enter a passcode on both the devices. Sometimes the passcode gives an error and you are unable to pair both the devices. For connecting them again, you have to reset the existing passcode to set another one.
Access menu on your mobile phone and select 'Bluetooth' from the 'Settings' options. Here you will find the devices that your cell phone is currently paired with. If you want to reset the passcode from your computer, click the Bluetooth icon on your computer's task bar tray. The list of paired devices will be visible to you.
Select the device for which you want to reset the passcode. If you are resetting from your cell phone, there will be an option 'Delete/reset PIN'. If the option is not available, simply 'Delete' the device from your cell phone. If you are resetting the passcode from your computer, right-click on the device icon and select 'Delete'.
Pair the two devices again. You will be asked to set a new passcode on the two devices before a connection can be established. Set the new passcode.