FourStroke Download link:FourStroke | OBD2 Elm Scanner on the App Store (apple.com)

NOTE:
Just enable Bluetooth settings on your iOS device.
DO NOT Need to connect Bluetooth Name on iOS device.
Then connect the Bluetooth device name in the OBD app setting.

Step1:
Open the app and click on "Connection".





Step2:
Select "Bluetooth LE(4.0)" for the connection method.





Step3:
Click on the button to the right of Bluetooth LE (4.0) to select the connected device.





Step4:
Select "vLinker FD-IOS".





Step5:
Connected successfully.