Three Steps to Install ELM327 Bluetooth Scanner on Android Phone/Tablet.
STEP 1: Turn ON Car Ignition and Then Plug in ELM327 Bluetooth Scanner into Cars Port
FIRST Turn ON cars ignition (one position before engine starts). And only then…
Plug ELM327 Bluetooth scanner into cars connector.
STEP 2: Pair ELM327 Bluetooth Device to Phone/Tablet
Touch Settings 
» Wireless & Networks » Check the Bluetooth box and go to » Bluetooth Settings.
From here — scan for devices and ELM327 Bluetooth scanner will show up as either: ELM, ELM327, CAN, OBD, etc.
When you’re asked for passcode to pair, enter: 6789
If “6789″ doesn’t work, then try “1234” or “0000“.
Done!
STEP 3: Launch the OBD App
Launch the OBD app you’ve downloaded from — and connect to ELM327. This is usually done in “Settings” within the App.
Example of typical Android OBD app.