What Is OBD2 and How Does It Work?
What OBD2 (On-Board Diagnostics) is, which cars have it, where the OBD2 port is, and what you can read with an app.
Updated: November 13, 2026
OBD2 (On-Board Diagnostics, 2nd generation) is a standard diagnostics system that continuously monitors a vehicle's engine and emissions-related systems. When a problem is detected, it stores a trouble code and turns on the check-engine light.
Which cars have it?
The OBD2 standard is generally found on petrol cars from 2004 and diesel cars from 2008 (Europe/EOBD) and on most newer models. The vehicle has a standard 16-pin trapezoidal port.
Where is the OBD2 port?
The port is usually under the steering wheel, near the glovebox or in the lower panel. An OBD2 adapter plugged in here connects to the vehicle's data bus (CAN).
What can you read?
- Trouble codes (DTCs) and their explanations
- Live data: RPM, temperatures, fuel trims, boost pressure
- Readiness monitors and emissions-test readiness
- Vehicle info (VIN, calibration IDs)
AutoMulti reads this data with an ELM327-based OBD2 adapter and interprets it with AI. For more, explore our trouble code dictionary.
Related codes
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