California smog check and OBD codes
California does not just sniff the tailpipe. It plugs into the OBD-II port and reads your monitors. That changes what you have to fix and in what order.
How the test actually works
- The station reads your OBD-II port first. A commanded-on check engine light ends the test before it starts. There is no tailpipe reading to argue about.
- Readiness monitors have to be complete. Each monitor is a self-test the computer runs during specific driving conditions. Clearing codes resets them all, and a car with incomplete monitors is rejected even with no fault present.
- Visual inspection still applies. A replacement catalytic converter on a California-registered car has to be CARB-approved for that application and carry an executive order number. A generic converter fails the visual even if the emissions reading is clean.
- Only then does the tailpipe test run, and only on vehicles new enough to need it.
Codes in our data that fail a smog check
These are the codes whose risk table in our data layer explicitly lists a failed emissions test. It is not a complete list of every code that fails a smog check — it is the list we can back with our own data.
What this page does not have yet
A per-vehicle CARB-compliant parts list, executive order numbers, and the cost of a California-legal converter are not on this page. Those need a data source we can cite, and we have not ingested one. We would rather leave the section out than print a part number that turns out to be a 49-state unit.
Common questions
Does a check engine light fail a California smog check?
Yes. A commanded-on check engine light is an automatic fail. The station cannot run the test until the light is off and the monitors have completed.
Can I clear the code and pass?
Not immediately. Clearing codes resets the readiness monitors, and a car with incomplete monitors is rejected. You have to drive enough cycles for them to set again, and a real fault will return before that happens.
Does a California car need a CARB-approved catalytic converter?
For a car registered in California, a replacement converter has to be CARB-approved for that application and carry an executive order number. A generic 49-state converter will fail the visual inspection.