Information for Motorists: Emissions
Learn more about vehicle emissions and their
effects on our environment: visit the Air & Climate home page of the Department
of Environmental Protection (MassDEP) website.
What is readiness?
A vehicle’s on-board diagnostics (OBD) computer monitors engine, transmission, fuel system, and emissions control performance. Up to eleven “readiness monitors” or software routines continuously or periodically check these major systems and components under specific operating conditions. If enough monitors have not completed their checks by the time an inspection station connects to a vehicle’s OBD system for an emissions test, the vehicle is “not ready” and will not pass its inspection or re-test.
To pass the emissions test:
- 2000 and older model year vehicles may have a maximum of two (2) “not ready” non-continuous monitors.
- 2001 and newer model year vehicles may have a maximum of one (1) “not ready” non-continuous monitor.
- If the vehicle failed the emissions test with a catalytic converter-related diagnostic trouble code, the vehicle’s catalyst monitor must be “ready” to pass the retest.
Certain common repairs or maintenance procedures can temporarily interrupt power from a vehicle’s battery to its OBD computer, leaving monitors “not ready” for an emissions test because the power loss has cleared all diagnostic results from the computer’s memory. After power is restored, the computer needs to monitor various driving conditions long enough to run the required number of checks again, determine whether emissions-related systems or components are performing correctly, and store this information to be “ready” for a state emissions test.
Until the computer is “ready” for OBD emissions testing, the vehicle will fail its initial inspection or be turned away from a re-test. There may be nothing wrong with the vehicle; the computer simply needs to complete its checks. One week of combined highway and city driving is normally enough to reset the system and provide an accurate reading of vehicle performance.
Massachusetts has established a network of Motorist Assistance Centers (MACs) to help vehicle owners and their repair technicians diagnose emissions problems with vehicles that fail their initial inspections. MACs are conveniently located across Massachusetts.
Your vehicle may be referred to a MAC if:
- The emissions test analyzer identified something unusual in your inspection that should be verified before you spend money on repairs;
- Your vehicle is having repeated problems with readiness that indicate you may need additional assistance;
- Your vehicle has been selected for a program evaluation inspection; or
- You have a specialty vehicle, such as a kit car.
If your vehicle has been referred to a MAC, it will need to be evaluated there before you can return it to an inspection station to complete the inspection process. If you want to apply for an Economic Hardship Failure Extension or a Waiver of Emission Standards, your vehicle will need to be evaluated at a MAC to confirm that it meets the requirements. Call the Motorist Hotline at 1-866-941-6277 for more information or to make an appointment at a MAC that is convenient for you.
Motorist Assistance Center Locations and Map