Hi @lorenzo1, welcome to the forum 
I’d recommend you have a read of this comment (and the post it’s in as relevant).
00 00 is a payload length of 0 bytes. The following two bytes BD 04 ends up as message ID 1213 ((0x04 << 8) + 0xBD), which is a processor temperature message from the sonar, which should have two bytes of payload but apparently doesn’t in this case.
The next message is voltage_5, and for some reason also has no payload. Both messages have correct checksums, so I assume you’re using a firmware that doesn’t properly support those messages.
Can you confirm which firmware version you’re using?
If the “Current Firmware” is not already listed as 3.28 then I’d recommend you select that from the dropdown menu and update to it.
Is there a particular reason you’re looking at individual bytes for this? We provide multiple libraries that can be used to parse and send ping protocol messages in a convenient manner: