Emissions. A vehicle that fails its emissions test must be repaired and pass a re-test within 60 days of its initial inspection. Give the Vehicle Inspection Report (VIR) you received from the inspector to your repair technician, who can use the information it provides to diagnose your vehicle's emissions control problem(s). Need a copy of your Vehicle Inspection Report? Get a reprint here. If the inspector also gave you an Emissions Repair Form, be sure to have the repairer complete it and then return the form to the inspector when you take your vehicle back for its re-test. Check with your repairer to see if he or she has filled this form out on-line for you. If so, you will not need to return the form to the inspector.
There are two important reasons for completing repairs immediately:
It is technically illegal to operate your vehicle before fixing safety defects identified during an inspection.
Emissions control problems can significantly reduce gas mileage, and may cause long-term damage to your vehicle that will make repairs more expensive.
Keep your repair receipts inside your vehicle as proof that repairs have been made until your vehicle passes its re-test. This is especially important if your vehicle failed its initial safety inspection.
Sometimes, repairs don't fix the problem(s) that caused your vehicle to fail its emissions test or estimated repair costs are extremely high because a major component needs to be rebuilt or replaced. In these cases, you may still be eligible for a passing sticker. If your private passenger vehicle or OBD-equipped motor home:
Failed its emissions test and was fixed by a Registered Emissions Repair Technician but fails its retest, you may be eligible for a Waiver of Emissions Standards [link] and a passing sticker that will be valid until your vehicle's next annual inspection.
Needs a major and costly repair to pass its emissions test (e.g., transmission replacement or engine overhaul), you may be eligible for an Economic Hardship Repair Extension and a one-time, one-year sticker to continue operating the vehicle while you save for repairs or look for a replacement.
To get either a waiver or an extension, you will need to bring your vehicle and its inspection and repair records to a Motorist Assistance Center (MAC) for evaluation. The MAC will provide you with an authorization so the inspection station that failed your vehicle can then issue you a passing sticker, or will explain how your vehicle does not meet waiver or extension requirements. Your Vehicle Inspection Report will contain instructions on how to schedule an appointment at a MAC.
There are no waivers or extensions for any safety defects or for emissions problems with commercial vehicles.
Massachusetts uses two types of emissions tests: On-Board Diagnostic (OBD) for most vehicles and Snap Acceleration Opacity for heavy duty vehicles that are not equipped with OBD systems.
On-Board Diagnostic (OBD) tests are given to:
- Model year 1996 and newer passenger cars, light trucks and SUVs
- Model year 1997 and newer light-duty diesel vehicles (8,500 pounds or less)
- Model year 2007 and newer medium-duty vehicles (8,501 to 14,000 pounds)
- Model year 2008 and newer medium-duty diesel vehicles (8,501 to 14,000 pounds)
The Massachusetts Vehicle Check on-board diagnostic (OBD) emissions test is designed to ensure that your vehicle keeps running as cleanly as it was designed to run, which in turn protects the air we breathe.
The OBD test typically takes about 3 minutes. The inspector connects your vehicle's on-board computer to an analyzer in the station, and then downloads engine and emissions control data. The analyzer checks several OBD system functions:
Communication. Does your vehicle's OBD system communicate with the analyzer? If your vehicle's OBD system cannot communicate with the station's analyzer, the OBD system must be repaired before the emissions test can be completed.
Readiness. Is your vehicle's OBD system "ready" to be tested? As your vehicle drives, the OBD system checks the performance of various emissions-related components and systems. If the OBD system has not performed enough of these self-checks, your vehicle is "not ready" for an emissions test.
OBD Vehicles Exempt from Readiness Checks. Some 1996 and newer vehicles exhibit unique testing characteristics that prevent them from receiving a complete OBD emissions test. These particular vehicles will skip over the readiness checks and go directly to the MIL (malfunctioning indicator light) check.
Diagnostic Trouble Codes (DTCs). Why would the OBD system turn on the Check Engine light? These indicators are diagnostic trouble codes that indicate which systems or components are not performing as designed. Reviewing these codes is the first step in diagnosing an emissions-related problem. These codes, along with other information in the OBD system, help guide emissions repair technicians to faulty parts and take the "guess-work" out of the process.
Check Engine Light. Is the Check Engine light (sometimes labeled as "Service Engine Soon") turned on? When this light is turned on, it indicates that one or more components of your vehicle's emission control system is not working as it was designed to work, and repairs are needed. If the light does not turn on when the OBD system tries to turn it on, this problem must be corrected.
The results are printed on the Vehicle Inspection Report (VIR), which the inspector will give you when the inspection is finished.
If your vehicle passes both its OBD emissions test and its safety inspection, it is issued a new sticker. If OBD detects a problem with your vehicle (generally indicated in advance by an illuminated "Check Engine" or "Service Soon" light), your vehicle will fail its inspection and will need to be repaired.
The most common causes of emissions test failures include:
- Malfunctioning components that regulate fuel/air ratio, such as oxygen sensors
- Exhaust gas recirculation (EGR) valves
- Engine misfire
- Catalytic converters
- Evaporative controls, including poor-fitting gas caps
Sometimes, a vehicle will fail or be turned away from inspection because its OBD system is "not ready." This simply means that the OBD system did not have enough valid data to evaluate the vehicle's emissions control system. This may be because the vehicle's battery was disconnected recently, perhaps while repairs were being made to the alternator, starter, electrical system, engine or transmission. Usually, a week of combined highway and city driving will reset the OBD system so that it will be ready for testing.
The VIR provides information that a repair technician can use to diagnose your vehicle's problem, fix it before it causes more air pollution, and spare you from more expensive repairs down the road.
Emissions Testing of Heavy Duty Diesel Vehicles
"Snap acceleration opacity" tests are used for diesel trucks, buses and other heavy-duty vehicles that weigh more than 10,000 pounds (Gross Vehicle Weight Rating) but are not equipped with OBD systems.
In this test, the inspector uses an opacity meter or "smoke meter" to measure the smoke from the vehicle's exhaust pipe. The darker the smoke, the more the vehicle is polluting and the higher its opacity reading will be.
The inspector first secures the vehicle safely (so it cannot move) and tests to ensure that its engine governor is functioning properly. Then the inspector presses on the throttle to bring the engine up to its maximum governed revolutions per minute (RPM) several times - first to remove loose soot from the exhaust pipe, then to measure the opacity of the vehicle's emissions.
Readings from the final three acceleration "snaps" are averaged. The final average is compared to the emission standard for the model year and type of vehicle. Newer vehicles have more sophisticated emission controls, and must meet stricter standards.