Guide Updated 2026-10-30
Smog check glossary, every California smog term in plain English
This glossary explains every California smog check term, such as OIS, BAR 97, ASM, TSI, STAR and CAP, and links each one to a full guide.
How to use this glossary
Smog check talk is full of short forms. BAR, the state agency, uses them on its pages, on your report and in its rules. This page explains 41 terms in plain words. Each one links to the guide that covers it in depth.
The terms below are grouped by topic. Use your browser search to jump to a term. The two tables here are quick lookups. First, which test uses which term. Second, the money terms.
| Car | Test it gets | System |
|---|---|---|
| Gasoline and hybrid, 2000 and newer | OBD inspection | OIS |
| Diesel, 1998 and newer, 14,000 lbs or less | OBD inspection | OIS |
| 1976 to 1999 in an enhanced area | Treadmill tailpipe test (ASM), with idle test if it cannot use the treadmill | BAR 97 |
| 1976 to 1999 in a basic or change of ownership area | Two speed idle (TSI) | BAR 97 |
| 1976 to 1995 | Also fuel cap, timing, EGR and LPFET checks | BAR 97 |
The test and the equipment
- OIS (OBD Inspection System, also written BAR OIS)
- The state approved system a station uses to test 2000 and newer gasoline cars, all hybrids and 1998 and newer diesels. The inspector reads the car computer instead of putting a probe in the tailpipe. It runs on a data acquisition device, a palm scanner for the inspector and the Cal-VIS software. What happens during a smog check
- BAR 97 (BAR 97 Emissions Inspection System)
- The older tailpipe testing system. BAR says it is required to inspect most model year 1999 and older cars. It measures what comes out of the exhaust. What happens during a smog check
- ASM (Acceleration Simulation Mode)
- A tailpipe test where the car runs on a treadmill called a dynamometer. Most 1976 to 1999 cars in enhanced areas get it, because it measures nitrogen oxides. If a car cannot go on the treadmill, it gets the two speed idle test instead. Smog check areas
- TSI (Two speed idle)
- A tailpipe test taken with the engine idling and again at a higher speed. Basic areas and change of ownership areas use it for 1976 to 1999 cars. Smog check areas
- LPFET (Low Pressure Fuel Evaporative Test)
- A pressure check of the fuel vapor system. It applies to most 1976 to 1995 cars. A few designs are excused, such as dual tank cars and cars with no adapter. Why cars fail
- OBD (On Board Diagnostics)
- The self test system in your car computer. It watches emissions parts and stores trouble codes. Check engine light
- MIL (Malfunction Indicator Lamp)
- The official name for the check engine light. It should light with the key on and engine off and go out with the engine running. A car with it on does not pass. Check engine light
- DTC (Diagnostic Trouble Code)
- A code the computer stores when it finds a problem, like P0420 for the catalyst. Check engine light
- PDTC (Permanent Diagnostic Trouble Code)
- A code that cannot be erased by a scan tool or by disconnecting the battery. The car clears it only after it confirms the problem is gone. BAR added a check for 2010 and newer cars on July 1, 2019. A stored one fails the car unless the car has done 15 warm up cycles and 200 miles since codes were cleared. Check engine light
- Readiness monitors (OBD self tests)
- Tests the computer runs on its own, one per system. After a battery disconnect they reset and must run again. Most gas cars may have only the evaporative monitor incomplete. Readiness monitors
- Catalytic converter
- The exhaust part that cleans harmful gas. Replacement ones must be original or CARB approved and show an EO number. Catalytic converters and smog
- EO number (Executive Order number)
- The CARB approval number printed on an aftermarket part. For converters it starts with a D. The inspector checks it against CARB's list. Catalytic converters and smog
- VIR (Vehicle Inspection Report)
- The report the station prints after every smog check. It shows the result, the reasons for a fail, open safety recalls and the certificate number. The inspector signs it. Smog check history lookup
- Certificate of compliance
- The electronic smog certificate issued on a pass. The station sends it to DMV and it is valid for 90 days. DMV authorized stations
Stations and who runs the program
- BAR (Bureau of Automotive Repair)
- The state agency that licenses smog stations and inspectors and runs the Smog Check program. It is part of the Department of Consumer Affairs. DMV authorized stations
- CARB (California Air Resources Board)
- The state air agency. It approves aftermarket emissions parts, runs the Clean Truck Check and manages part of EFMP. Clean Truck Check
- STAR (Smog Check STAR program)
- A voluntary program for stations that meet higher performance standards. It began January 1, 2013 and replaced Gold Shield. Only STAR stations or a Referee can certify directed vehicles and gross polluters. STAR smog check stations
- Directed vehicle
- A car BAR sends to a STAR station. Your DMV notice says Smog Certification Required at a STAR station. Some are chosen by a high emitter profile and about 2% are chosen at random. STAR smog check stations
- FPR (Follow up Pass Rate)
- A score from 0 to 1 that BAR gives stations and inspectors. It checks whether cars a station or inspector certified last cycle are now passing at a higher than expected rate. It is a long term measure. Above 0.50 is better than average and 0.40 is the minimum to apply for STAR. It updates in January and July. STAR smog check stations
- Test only station
- A station licensed to inspect but not repair, apart from free minor fixes. DMV authorized stations
- Test and repair station
- A station licensed to inspect and to repair cars that fail. DMV authorized stations
- Repair only station
- A station licensed to repair but not to issue a smog certificate. DMV authorized stations
- Referee (Smog Check Referee)
- A state contracted facility that handles disputes, repair cost waivers, unusual cars, engine swaps, kit cars and catalytic converter labels. It does not repair cars. Waiver and the Referee
- Program area (Enhanced, basic and change of ownership)
- The three kinds of area. Enhanced and basic areas need a check every other year. Change of ownership areas need one only when a car is sold or first registered in California. Smog check areas
- Biennial
- Every other year, the timing of a renewal smog check. Do I need a smog check
Money and help
- CAP (Consumer Assistance Program)
- BAR's program that pays toward repairs for income eligible owners of cars that failed, up to $1,450 for 1996 and newer cars. It also buys cars for retirement. CAP repair assistance
- EFMP (Enhanced Fleet Modernization Program)
- A CARB program managed with BAR. Its retirement option pays income eligible owners $1,500 for a car even if it passes smog. CARB also runs a scrap and replace part of the program. Vehicle retirement program
- Smog abatement fee
- A yearly fee on newer gas cars that replaces the renewal smog check in the first eight model years. It is $20 a year for years one to six and $25 for years seven and eight. Smog abatement fee
- Smog transfer fee
- An $8 fee the buyer pays to DMV when a gas car four model years old or newer changes hands in place of a smog check. Buying and selling
- Certificate fee
- The $8.25 state charge when a car passes. It is shown apart from the inspection price. Cheap smog checks
- Repair cost waiver
- A way to postpone the smog requirement up to two years after you spend at least $650 on eligible repairs and the car still fails. The Referee issues it. Waiver and the Referee
Bad cars and bad tests
- Gross polluter
- A car whose tailpipe emissions exceed the gross polluter limits. It can only be certified at a STAR station or by a Referee. It may still qualify for CAP or a waiver. STAR smog check stations
- Tampered
- Any emissions part that is missing, modified or disconnected. It fails the visual check. Catalytic converters and smog
- Clean piping
- BAR calls it a method where another car's properly working exhaust, or another source, is used to produce passing readings and fraudulently issue certificates to cars that are not compliant or not present. It applies to tailpipe tests on older cars. Smog check history lookup
- Clean plugging
- BAR calls it a method where another car's working OBD system, or another source, is used to create passing data or diagnostic information so a certificate is issued to a car that is not compliant or not present. Smog check history lookup
- Clean scanning
- A street name for faking the OBD scan of a test. The BAR documents we reviewed describe the same idea as clean plugging and do not define clean scanning separately. Smog check history lookup
- Certificate blocking
- A BAR power to block a certificate right away when it has enough evidence of a fraudulent inspection. Smog check history lookup
Heavy duty and special cases
- GVWR (Gross Vehicle Weight Rating)
- The most a vehicle may weigh with load and passengers, set by the maker. Smog Check covers diesels at 14,000 lbs or less. Clean Truck Check
- Clean Truck Check
- CARB's test program for diesel and alternative fuel vehicles over 14,000 lbs. Clean Truck Check
- PZEV (Partial Zero Emission Vehicle)
- A very clean car class with extra long emissions warranty, 15 years or 150,000 miles, and a 10 year hybrid battery warranty. Hybrid and EV smog check
- Engine change
- Installing an engine that is not the one the car came with. It needs to meet the engine change rules and may need the Referee. Waiver and the Referee
Money terms in one table
| Money term | Amount | Who gets it |
|---|---|---|
| Certificate fee | $8.25, only on a pass | The state |
| Smog transfer fee | $8, gas cars four model years old or newer | DMV |
| Smog abatement fee | $20 a year in years 1 to 6, $25 a year in years 7 and 8 | The state, with registration |
| Repair cost limit | $650 | Level at which a waiver opens |
| CAP repair help | Up to $1,450 for 1996 and newer cars, $1,100 for 1976 to 1995 | Paid toward repairs |
| CAP and EFMP retirement | $1,350, $1,500 or $2,000 depending on the path | Paid to the owner |
Looking for a station? Use the station finder, then check the license with the license guide. For the rules by year read do I need a smog check.
Questions people ask
What does smog check OIS mean?
OIS is the OBD Inspection System, the BAR approved equipment that tests 2000 and newer gasoline cars, hybrids and 1998 and newer diesels by reading the car computer.
What is BAR 97?
It is BAR's older tailpipe testing system. BAR says it is required to inspect most model year 1999 and older cars.
What is the difference between ASM and TSI?
ASM puts the car on a treadmill and measures emissions under load. TSI measures them with the engine idling and at a higher idle speed. Enhanced areas use ASM for most 1976 to 1999 cars and other areas use TSI.
What does STAR mean on my DMV notice?
It means your car is a directed vehicle. The smog check must be done at a STAR station, one that meets higher BAR performance standards.
What is a VIR in smog check?
A VIR is the Vehicle Inspection Report. The station prints it after each smog check with the result, reasons for a fail, open recalls and the certificate number.
What is a gross polluter?
It is a vehicle with tailpipe emissions above the gross polluter limits. Only a STAR station or a Referee can certify it.
What are clean piping and clean plugging?
They are forms of smog check fraud. Clean piping uses another car's clean exhaust to fake a pass and clean plugging uses another car's working OBD data.
What does PDTC mean?
It means permanent diagnostic trouble code. It cannot be cleared by a scan tool or by disconnecting the battery, and a stored one can fail a 2010 or newer car.
What is EFMP?
It is the Enhanced Fleet Modernization Program, run by CARB with BAR. Its retirement option pays income eligible owners $1,500 for a car, even if it passes smog.
What does FPR stand for?
FPR is the Follow up Pass Rate, a score from 0 to 1 that BAR gives stations and inspectors. Above 0.50 is better than average.