OBD stands for “On Board Diagnostics.” New cars (including the 1997 Nissan pick-up I had) have the OBD2 system where older cars, like my 1991 Nissan pick-up, have the OBD1 system. My old truck still requires a probe up the tailpipe but newer cars with OBD2 systems use the vehicle’s sensors to read all emission conditions so no probe is required. If your “Check Engine” light is on before an emissions test, the vehicle will fail even before the test facility plugs in the emission test computer to the OBD system computer.
If you have a “Check Engine” light, you have the OBD2 system.