I just want to share my experience based on my recent experience with ELM 327 Bluetooth dongle devices.
Here is how you can find either it's genuine one or cloned(There are some bad clone and some good clone as well)
Bad Clone devices:
If the MAC address of your adapter starts with the numbers 66:35:56: ... or 88:35:56:...(for example, 66: 35: 56: 78: 90: AB) or 00:00:00:00:00:01or AA:BB:CC:11:22:33 or some other "strange looking" addresses- be prepared that this adapter could fail to connect, will not support all protocols, fail to read some data and what's more, they can cause problems with your car.
Good Clone devices:
There are also some adapters that might be almost good while working with single ECU and short commands, but cold fail to get reliable results for cars with 2 and more ECUs and "long" commands like VIN or DTC readings. One of this could have following MACs:
00:1D:A5:68:98:8A or 00:1D:A5:68:98:8C
As well, there might be problems with other "no-name" Chinese adapters marked ELM327 v2.1.
You can use the ELM327 Identifier app as well to identify the supported commands.
contents copied from here.
