All 2002 - 2023 model year vehicles subject to emissions inspections will receive a two-part inspection:

- An OBD test to check a vehicle's emissions control performance history;

- A visual inspection of the catalytic converter to check for tampering or removal.

All 1996 and newer model year vehicles have a built-in on-board diagnostic (OBD) computer system.

The OBD system monitors, among other things, the performance of your vehicle's emissions controls system to make sure it is functioning properly.

The OBD test reviews your vehicle's emissions control performance history.

The inspector will attach the testing equipment to a vehicle's data link connector (or DLC) to read specific codes from the vehicle's computer memory. The DLC is usually located inside the vehicle on or near the dashboard.

Most well-maintained vehicles will pass inspection the first time. However, if a vehicle has an emissions-related problem or malfunction, the testing equipment will read one or more diagnostic trouble codes (DTCs) indicating the nature of the malfunction.

A vehicle's on-board computer system will tell whether the emissions control system is working properly or not. If it is not working properly, it is likely that the vehicle is exceeding emissions levels.

If the "Check Engine" or "Service Engine Soon" light is on, a vehicle will not pass the inspection. This is an indication of an emissions control system problem.

Your vehicle inspection report (VIR) will list the first five diagnostic trouble codes (DTCs) that indicate the general area of the emissions control systems that do not pass inspection. Along with a diagnostic analysis, DTCs help the technician determine what repairs are necessary. Ask for an estimate and understand what work will be performed prior to authorizing repairs. Also ask if the repairs are covered under warranty.

The "Check Engine" light may illuminate indicating something as minor as a loose fuel cap, or a major emissions control component failure.

If a DTC listed on the VIR indicates a fault with the vehicle's "Evaporative System," try tightening the fuel cap until it clicks, then drive the vehicle for a few days to see if the OBD system turns the light off.

A transmission code is directly related to the emissions control system. A vehicle's on-board computer will illuminate the "Check Engine" light if a problem with the transmission is detected. A diagnostic analysis will help identify emissions-related components that need repair. A transmission malfunction can indeed prevent a vehicle from running efficiently, therefore increasing emissions.

If the "Check Engine" light remains on, you will need to have the problem properly diagnosed and your vehicle repaired prior to retest. The retest is free if you return to the original inspection station within 30 calendar days.

Make sure to allow ample driving time after repairs for the vehicle to complete its drive cycle and the OBD computer to become "Ready" for testing (one to two weeks, including some highway driving).

Motorists should beware of offers to turn the "Check Engine" light off in an attempt to pass the OBD test without making repairs. If the light has been turned off without making necessary emissions-related repairs, it will come back on and the vehicle will not pass the test. The VIR will read "Fail" for being "Not Ready."

If the "Check Engine" light is flashing, have your vehicle serviced immediately to avoid costly damage of your vehicle's main emissions control component, the catalytic converter.

Contact your vehicle manufacturer or repair technician and inquire about recalls, manufacturer-applied extended warranties, and technical service bulletins (TSBs) regarding the emissions control system (research by your VIN).

If emissions-related repairs meet or exceed $1,146 for 2025 registration, you may qualify for a Repair Waiver. Visit a GCAF Customer Service Center for assistance.

Your vehicle's on-board diagnostic (OBD) computer must be "Ready" so it can conduct its self-test before an emissions inspection is performed.

If your vehicle's OBD computer is "Not Ready," it will fail the inspection.

A "Not Ready" code may be due to recent vehicle maintenance or your vehicle's battery may have been replaced or disconnected.

Your vehicle must be driven under certain conditions for the computer to be "Ready." Some vehicle manufacturers provide driving procedures to "Ready" your vehicle.

Contact your vehicle manufacturer or qualified service technician for more information.

The only information accessed during an OBD test is the emissions control performance history of a vehicle.

The OBD test cannot detect speed or other driving history information.

There are two main reasons why a 2002 or newer model year vehicle may not pass the OBD test:

- There is something wrong with your vehicle's emissions control system and it needs to be repaired. You will receive a copy of your vehicle inspection report (VIR) and Emissions Repair Form from your inspector. Take these with you to a repair facility. The VIR will indicate the general area of the problem, which will assist your repair technician in determining appropriate repairs. The emissions inspection is not a diagnostic analysis.

- Your vehicle's OBD computer is "Not Ready," so the test cannot be completed. While this does not necessarily mean that your vehicle has a problem, it does indicate that your vehicle's OBD computer has not yet completed its self-tests (or become "Ready").

A vehicle's on-board diagnostic (OBD) computer may indicate "Not Ready" as a result of recent maintenance or if the vehicle's battery has recently been replaced or disconnected. No repairs or diagnostic analysis may be needed if a vehicle fails the initial inspection due to being "Not Ready."

The most common reasons for "Not Ready":

- The vehicle's battery was recently disconnected or replaced.

- The vehicle's battery is in a low state of charge.

- The vehicle was recently serviced and a scan tool was used to clear diagnostic trouble code (DTC) information.

- The vehicle's OBD computer requires a software update.

- A pending problem with the emissions control system has yet to turn on the "Check Engine" light.

- An improperly installed aftermarket system - examples include, but are not limited to, a CD player, security system, navigation system, and/or satellite radio.

In order to "Ready" a readiness monitor, the vehicle needs to operate in a way that will allow the emissions control system to be evaluated. For most vehicles, setting the readiness monitors to "Ready" will require the fuel level in the fuel tank to be between 25 percent and 75 percent and a cold start. A cold start means the vehicle should not be operated for approximately eight hours, allowing the vehicle's engine temperature to equalize with the outside air temperature. After a cold start, the vehicle should be operated at normal conditions for one to two weeks with some highway driving.

If after completing the above steps the vehicle's readiness monitors are still reading "Not Ready," check the following components:

- The wiring on any installed aftermarket system to ensure there is no interference with the OBD computer or battery.

- All fuses.

- The vehicle's thermostat; especially the temperature of the coolant/antifreeze.

- All recalls, technical service bulletins (TSBs), extended warranties related to the emissions control system and the OBD computer.

- Have a diagnostic analysis performed with an OBD II generic scan tool; connecting to the data link connector (DLC) under the dash, not under the hood.

- The vehicle was recently serviced and a scan tool was used to clear diagnostic trouble code (DTC) information.

- The vehicle's OBD computer requires a software update.

- A pending problem with the emissions control system has yet to turn on the "Check Engine" light. Check for pending codes using a scan tool.

- An improperly installed aftermarket system - examples include, but are not limited to, a CD player, security system, navigation system, and/or satellite radio.

You may be able to obtain a copy of your vehicle's "drive cycle" from your vehicle manufacturer or other source. You may also find information regarding your vehicle's "drive cycle" in the owner's manual.

If emissions-related repairs meet or exceed $1,146 for 2025 registration, you may qualify for a Repair Waiver.

Return to the original inspection station for a free retest within 30 calendar days of initial test. The 30 days includes the day of your first test and expires at the time of day of the original test.

Note: Federal law requires that the OBD computer and catalytic converter on 1995 and newer vehicles be warranted by the manufacturer for eight years or 80,000 miles.

Once the vehicle becomes "Ready," the OBD computer may detect emissions-related problems. If so, the "Check Engine" light will illuminate indicating that repairs are required. You should proceed with the proper repairs before using your free retest.

Note: Before a retest can be performed, you must provide the failed vehicle inspection report (VIR) and completed Emissions Repair Form, which should be filled out by your repair technician. If self-repairs are conducted by the vehicle owner, only the cost of parts (not labor) should be documented on the Emissions Repair Form.

The inspector should attempt to test the vehicle several times.

If your vehicle has had an after-market radio, CD player or security system installed, make sure that that the wiring is not interfering with connection to the vehicle's computer or battery system.

Research recalls, technical service bulletins (TSBs) and manufacturer applied extended warranties to determine if there are any recommended repairs regarding the emissions control system.

Have a diagnostic analysis performed using an OBD generic scan tool; connect to the data link connector (DLC) under the dash, not under the hood.

Federal law requires that the OBD computer and catalytic converter on 1995 and newer vehicles be warranted by the manufacturer for eight years or 80,000 miles.

To qualify for a Repair Waiver, the cost of emissions-related repairs must meet or exceed $1,176 for 2026 registration. The Repair Waiver limit is adjusted annually according to the Consumer Price Index.

DLC or Data Link Connector - The location where the OBD testing equipment is connected to a vehicle to perform an inspection. It is usually located on or near the dashboard of 1996 and newer model year vehicles.

MIL or Malfunction Indicator Light - If a vehicle's MIL (or "Check Engine" light) is illuminated, a vehicle will not pass the OBD test. The motorist should take their vehicle to a repair technician.

OBD or On-Board Diagnostics - A vehicle's built-in computer system that monitors the emissions controls system.