Shift OBD Complete Download link : Shift OBD Complete 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 the Settings button in the bottom left corner. 





Step2:
Click on "Interface".





Step3:
Select "Bluetooth LE 4.0 & Carista".





Step4:
After selecting the correct device, return to the home page.





Step5:
Wait for the app to connect automatically.