Make sure the check engine light is off and any known issues are repaired; a lit MIL is an automatic fail.

Drive the car regularly and take a 15–20 minute freeway drive just before the test so the engine and catalytic converter are fully warmed up and monitors can run..

Most 2000 and newer gasoline vehicles are tested using the OIS (On-Board Diagnostic Inspection System), which reads the vehicle’s OBD-II data instead of using a tailpipe (BAR-97) dyno test.

The inspector checks for stored trouble codes, readiness monitor status, visual/emissions equipment issues, and may perform functional tests like gas cap or EVAP checks.

Disconnecting the battery or clearing codes resets all monitors to “not ready,” and the car may be rejected or failed until drive cycles complete.

Plan to drive the vehicle for several days to a couple of weeks under mixed conditions after any reset so monitors can return to ready before scheduling the smog test.

Most 2000 and newer gasoline vehicles are tested using the OIS (On-Board Diagnostic Inspection System), which reads the vehicle’s OBD-II data instead of using a tailpipe (BAR-97) dyno test.

The inspector checks for stored trouble codes, readiness monitor status, visual/emissions equipment issues, and may perform functional tests like gas cap or EVAP checks.

Bring your DMV registration renewal notice or registration card so the station can verify vehicle information and submit results electronically.

Bring any prior smog inspection reports or repair invoices if the visit follows a recent failure; these help the technician understand history and repairs.

Readiness monitors are self-tests your vehicle’s computer runs on systems like catalyst, oxygen sensors, EGR, and EVAP. For 2000 and newer vehicles in California, all monitors generally must be “ready,” with limited exceptions historically for EVAP; regulations are tightening so that all must be set for most vehicles.​

Disconnecting the battery or clearing codes resets all monitors to “not ready,” and the car may be rejected or failed until drive cycles complete.

Plan to drive the vehicle for several days to a couple of weeks under mixed conditions after any reset so monitors can return to ready before scheduling the smog test.

Review the Vehicle Inspection Report (VIR) the station prints; it lists reasons for failure and any codes or monitor issues.

Consider repair assistance programs like California’s Consumer Assistance Program if you qualify for help with emissions-related repairs or vehicle retirement.

Current California rules allow very little leeway; historically, 2000+ gas vehicles could have EVAP incomplete, but updated regulations now move toward requiring all monitors ready, with rare exceptions granted by BAR.

If your car shows multiple incomplete monitors at the station, you will likely need more driving or further diagnosis before it can pass.