In case you use a Wi-Fi adapter, you first have to set up a
Wi-Fi connection between your mobile device and your OBD-II adapter.
The Wi-Fi IP address of your mobile device should be static while connected
to the adapter. This enables your mobile device to use internet via Cell
Network and a Wi-Fi connection to the OBD-II adapter in parallel.
In order to set up a static IP address for your mobile device, you need to
know which IP address is used by the OBD-II adapter. An easy way is to check
the addresses which are automatically assigned by DHCP. Then the first two
entries are used for the static setup: there they have to be entered manually.
Here you can see how it looks with iOS 11:
Get IP Address and Subnet Mask from connection details
Change to Manual and enter IP Address and Subnet Mask
That's how it looks after changes are saved
And here you can see how it looks with iOS 10 and earlier:
Get IP Address and Subnet Mask from DHCP connection details
Select Static and enter IP Address and Subnet Mask
Please make sure that the remaining fields are left empty; otherwise the
Mobile Internet does not work!