About the Program: Why & What We Test


What happens when I bring my vehicle for inspection?

First, a state-licensed inspector will give your vehicle a brief visual inspection to make sure there are no conditions such as leaking gasoline that present an immediate danger to either the inspector or the general public. These conditions must be fixed before the inspection proceeds.

After passing the visual inspection, you then present your vehicle registration to the inspector. A vehicle must have an active registration and matching valid vehicle ID number (found in the left front side of the dashboard) to get an inspection. After the inspector checks that your registration is valid, you pay the inspector $35. Drivers are then asked to exit the vehicle and remain in the waiting area while the inspector administers the safety and emissions tests,


Emissions Tests

All vehicles that are registered in Massachusetts must receive a safety inspection each year. Vehicles listed below must also receive the following types of emissions tests each year:

On-Board Diagnostic (OBD) Test:

  • Model year 2002 and newer passenger cars, trucks and SUVs

  • Model year 2002 and newer light-duty diesel vehicles (with a Gross Vehicle Weight Rating or "GVWR" of 8,500 pounds or less)

  • Model year 2007 and newer medium-duty diesel vehicles (with a GVWR of 8,501 to 14,000 pounds)

  • Model year 2008 and newer medium-duty non-diesel vehicles (with a GVWR of 8,501 to 14,000 pounds)

Opacity Test:

  • Medium- and heavy-duty diesel vehicles (with a GVWR of 10,000 pounds or greater) not equipped with OBD systems

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 three 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.

To pass the emissions test:

  • 2002 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.

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.

For more detail about emissions inspections, please review the MassDEP Vehicle Emissions Inspection Regulations.


Safety Test

Safety inspections typically take about 12 minutes. In a safety test, the inspector looks for or tests 14 key areas:

1. Visual Overview

2. Brake Tests

3. Exhaust System

4. Steering and Suspension

5. Horn

  • Sound horn to test for adequate signal
  • The horn must be securely fastened to the vehicle

6. Glazing, Glass and Windshield Wipers

7. Rear View Mirror

  • Rear view mirror
  • Mirrors (General)

8. Lighting Devices

9. Tires and Wheels

10. Bumper, Fenders, and Fuel Tank

11. Altered Vehicle Height

12. Seat Belts

13. Airbags

14. Fuel Tank Cap

Hours & Location
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  • Amenities:
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