What Data is Available from OBD?

OBD-II offers a standard way to access many types of data, including:

  • Real-time parameters: RPM, speed, pedal position, spark advance, airflow rate, coolant temperature, etc.
  • Status of “Check Engine” light
  • Emission readiness status
  • Freeze frame: a “snapshot” of parameters at the time a trouble event has occurred.
  • Diagnostic trouble codes (DTCs).
  • Oxygen sensor test results
  • Vehicle Identification Number (VIN)
  • Number of ignition cycles
  • Number of miles driven with MIL on

The SAE J1979 standard is the ultimate source for this information. Some of it is available for free from Wikipedia.