What the SMOG Check program does
California uses SMOG inspections to verify that covered vehicles meet emissions standards. In practical terms, the program is meant to catch emissions-related problems before those issues keep adding pollution or get more expensive to fix.
When drivers usually need a SMOG check
For many drivers, the most common trigger is the every-other-year registration renewal cycle. Another common trigger is a vehicle sale or transfer. A qualifying vehicle coming into California from out of state can also need inspection before registration is completed.
Not sure if your vehicle needs one? See the full breakdown on the who needs a SMOG check page.
Two details that confuse people most
First, newer vehicles may be exempt from the physical inspection while still paying an abatement fee. Second, a STAR station is not the same thing as every other station. If DMV directs your vehicle to STAR, that part matters.
How to prepare for the test
Before you go in, make sure the check engine light is off, readiness monitors are set, and the vehicle has been driven enough to warm up. See the full preparation checklist on the how to pass a SMOG check page.
What if the vehicle fails?
A failed result usually means the vehicle has an emissions-related issue that must be corrected before it can pass. The next step may be a repair, a retest, a BAR Referee review, or a Consumer Assistance Program application depending on the situation. Read more on the what happens if you fail page.
The visual inspection component
Many drivers focus on the tailpipe test and forget that technicians also perform a visual inspection of emissions-related components. Missing, modified, or non-compliant parts can cause a failure even if the vehicle's emissions readings are fine.