Adapter guide
Use an ELM327 adapter with a laptop.
An ELM327-compatible adapter plugs into the car's OBD-II port and connects to your computer over USB or Bluetooth. This guide covers which adapters work, how to connect one on Windows, macOS and Linux, and what to try when it won't connect.
What you need
- Computer: Windows, macOS or Linux.
- Adapter: an ELM327-compatible USB adapter, or a Bluetooth Classic adapter that shows up as a serial port once paired.
- Car: an OBD-II port. In the US, that means most cars and light trucks sold from 1996 on.
Some low-cost Bluetooth adapters use only Bluetooth Low Energy. They never show up as a serial port, so DeepDiag cannot use them. Pick a USB adapter, or a Bluetooth adapter that pairs as a serial (COM) port.
Plug it in
- Find the port. The OBD-II port is usually under the dashboard, near the steering column.
- Plug the adapter in. Push it in until it is fully seated.
- Turn the ignition on. Start the engine, or turn the key to ON or RUN. Accessory mode is not enough.
Windows
Pair a Bluetooth adapter in your computer's Bluetooth settings first. It then shows up as a serial (COM) port: look for “Standard Serial over Bluetooth link” under Ports in Device Manager.
DeepDiag checks every COM port Windows lists, so it still finds a paired adapter that lands on COM21 or higher.
macOS
Pair a Bluetooth adapter in your Mac's Bluetooth settings first. It has to show up as a serial device.
DeepDiag looks for USB adapters at /dev/cu.usbserial* and /dev/cu.wchusbserial* (adapters with a CH340 chip), and for Bluetooth adapters at /dev/cu.OBD*. It also checks the other serial ports macOS lists, so a Bluetooth adapter does not need “OBD” in its name.
The app tries each cu. device first. The matching tty. device waits for a carrier-detect signal before it opens.
Linux
Pair a Bluetooth adapter first. It has to show up as a serial device.
DeepDiag looks for USB adapters at /dev/ttyUSB* and /dev/ttyACM*, and for Bluetooth adapters at /dev/rfcomm*. It also checks the other serial ports the system lists.
If it does not connect
- Check the adapter is fully seated and the ignition is on.
- Let auto-detection run.
- Unplug and replug the adapter, then try again. For Bluetooth, remove the adapter from your computer and pair it again.
- Try a USB connection if Bluetooth pairing is unreliable.
- Close any other scan tool that may be holding the adapter.
- Check the battery. A weak battery or a charging fault can cause dropped connections and incomplete scans. When the car reports a low system voltage, DeepDiag's live data shows a warning.
- Try a quality adapter if VIN or live-data reads keep failing.
A failed VIN read is common with inexpensive adapters, and the app still connects. Its own troubleshooting names OBDLink and Veepeak as examples of quality adapters. That is not a guarantee or an endorsement.
What DeepDiag does with it
Through the adapter, DeepDiag reads your trouble codes, shows live sensor data and checks emissions readiness. It explains the codes in plain language with AI and says whether it's a job you can do yourself. Every feature, reading codes included, needs an active Premium subscription.
Coming soon