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.
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.