What's included in a California smog check?
California's smog check program exists to keep the state's air clean and hold vehicles to a consistent emissions standard. The test itself is a specific checklist set by the Bureau of Automotive Repair (BAR), and a certified technician performs the exact same procedure whether you are in Concord, Sacramento, or San Diego. Here is what is actually covered.
1. Visual Inspection
The technician opens the hood and checks that every factory-required emissions component is still present and properly connected. That includes:
- Catalytic converter (original or CARB-approved replacement)
- Fuel cap (pressure tested for leaks)
- EVAP system hoses and canister
- EGR valve and related hoses
- PCV valve
- Air injection system (where applicable)
Missing, modified, or non-compliant parts mean an automatic fail — no matter how clean the emissions numbers look.
2. OBD-II Scan (2000 and newer gas vehicles)
For any gasoline vehicle from model year 2000 or newer, the technician plugs a BAR-approved scan tool into the OBD-II port. The tool pulls:
- MIL status — is the check engine light on? If yes, automatic fail.
- Stored diagnostic trouble codes — even pending codes can fail the test.
- Readiness monitors — the onboard tests the car's computer runs on itself. Too many "not ready" = fail.
3. Functional Inspection
A quick check that the check engine light works when the ignition is turned on (bulb check), that the ignition timing is within spec on older vehicles, and that the EGR system (where applicable) operates correctly.
4. Tailpipe Emissions Test (older vehicles only)
This is the step people picture. The vehicle is driven onto a dynamometer (rollers) and run at two steady speeds while a probe in the tailpipe measures hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). The state has a pass/fail threshold for each gas.
This applies to:
- Gasoline vehicles 1999 and older
- Diesel vehicles 1998 and newer (diesel got added to the program in 2010)
- Motorhomes (model-year dependent)
2000-and-newer gas cars skip the tailpipe test entirely because the OBD-II scan covers it.
5. Result Transmission
Pass or fail, the result transmits electronically to the DMV within minutes. A passing result at a STAR station also satisfies any DMV-directed STAR requirement. You get a printed certificate for your records.
Why does Super Station Concord get chosen for this?
We are STAR Certified, which means we can handle any test the DMV directs — including the ones many regular smog shops cannot. Our coupon price is $49.75, and we usually complete the visit in 20-30 minutes.