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OBD2 Diagnostic Interface with BLE and Display

How to Use the System

The system consists of two devices:

  1. OBD2 Station – plugged into the vehicle diagnostic port
  2. Display Station – receives data via BLE and presents it to the user

System Startup

Step 1 – Connect the OBD2 Station

  • Plug the device into the vehicle’s OBD2 port.
  • After a few seconds, the green LED will start blinking – this indicates proper CAN bus communication.

If the LED does not blink:

  • make sure the ignition is turned ON,
  • verify that the vehicle supports OBD2 over CAN.

Step 2 – Power the Display Station

  • Connect the device via USB power.
  • After startup, it will automatically begin scanning for BLE devices.
  • Once connected, a BLE icon will appear on the screen.

If the BLE icon does not appear:

  • ensure the OBD2 station is powered and connected,
  • check that both devices are within range (a few meters).

Displayed Data

The screen presents:

  • Current vehicle speed
  • Engine RPM
  • Instant fuel consumption
  • Average fuel consumption
  • Traveled distance
  • Fuel used
  • Current date and time

Reset Function

A Reset button is located at the bottom of the screen.

Pressing it resets:

  • average fuel consumption
  • traveled distance
  • fuel used

Measurement Units

  • Speed – km/h
  • Engine RPM – revolutions per minute
  • Driving fuel consumption – l/100 km
  • Idle fuel consumption – l/h

System Limitations

  • Not all vehicles provide all PID parameters.
  • Some newer vehicles may restrict access to certain data (e.g., intake temperature).
  • In older vehicles, fuel consumption may be calculated approximately (formula-based).

Requirements

The vehicle must:

  • have an OBD2 connector,
  • support CAN communication (ISO 15765-4),
  • have ignition turned ON.

Connection Architecture

  • OBD2 Station → BLE Peripheral (server)
  • Display Station → BLE Central (client)

The connection is established automatically after both devices are powered on.

Quick System Flow

Car → OBD2 → CAN → ESP32 → BLE → ESP32 → Display

Additional Information

The system operates in a closed ecosystem and does not require:

  • a smartphone,
  • a mobile application,
  • internet access.

Possible future extensions:

  • DTC reading and clearing
  • Extended diagnostic parameters
  • Historical data logging