Testing Procedures

Position 1

Picture of person exiting their vehicle and entering a booth

1. The inspector asks you to exit your vehicle and wait inside the booth while your vehicle is tested.


2. The inspector performs a tampering inspection on your vehicle. They make sure your vehicle has both a gas cap and a catalytic converter (if it was manufactured with both).  They also check for obvious fluid leaks, bald tires and other safety concerns that may prevent your vehicle from being tested.


3. The inspector enters the Vehicle Identification Number (VIN) into the computer so that the emissions standard for your vehicle can be pulled up and the vehicle identified. 

Position 2

Inspecting the car

OBD Test

If your vehicle is 1996-or-newer (gasoline) or 1997-or-newer (diesel), it will most likely be tested with On-Board Diagnostics (OBD II) technology.* A handheld reader device will be connected to your vehicle's data port to download emission control system performance codes.

If your vehicle's data port is inaccessible, your vehicle will receive a tailpipe test on the dynamometer.


Tailpipe Test

1. The vehicle is moved onto a dynamometer, a treadmill-like device, and a probe is placed in the tailpipe to collect gases.

2. The vehicle is driven at a constant speed between 24 and 26 mph in a simulation of actual driving conditions.

3. Tailpipe exhaust is analyzed to determine how much pollution it contains. Vehicles should complete this phase of the test between two and four minutes.

4. Vehicles that cannot be driven on the dynamometer because of weight, traction control or four-wheel drive are given an idle test.

*Some restrictions may apply.

Position 3

Getting back into the car

1. The vehicle is now driven from Position 2 to Position 3 and prepared for the gas cap pressure test. The inspector will remove your gas cap and connect it to a gauge that measures pressure. This ensures that gasoline vapor is not being lost from your tank. 


2. Once the testing is complete, the inspector will hand you your Vehicle Inspection Report and explain the results. 


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