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On-Board Diagnostics-II (OBD-II). Questions usually involve scan tools, their use and their compatibility, as well as how to interpret Diagnostic Trouble Codes (DTCs).

On-Board Diagnostics-II (OBD-II)

On-Board Diagnostics-II is a standard for vehicle self-diagnostic data capabilities as well as real-time data reporting capabilities.


The OBD-II standard allows for five different signalling (or data) protocols to be transmitted through the OBD-II interface. These are:

  • SAE J1850
  • PWM SAE J1850
  • VPW ISO 9141-2
  • ISO 14230 KWP2000
  • ISO 15765 CAN

OBD-II Scan Tools

Most modern scan tools are capable of reading the 5 different data protocols. Most are capable of resetting/clearing fault codes while more advanced tools are capable of setting ECU parameters, controlling other on board units such as ABS and Air Bags as well as real time monitoring and data logging of various engine parameters.

Further Reading

  • A list of PIDs can be found on Wikipedia.
  • A list of trouble codes can be found here.