General Information

On-board diagnostic systems (OBD) on 1996 and newer vehicles will be checked as part of Vermont’s annual vehicle inspection program. OBD technology benefits motorists, technicians, and our environment. It’s good for motorists because it monitors the vehicle’s performance every time it is driven and identifies problems immediately,

allowing service to be done before more serious problems develop. It’s good for technicians because it helps accurately diagnose problems, allowing for efficient and proper repairs. And it’s good for our environment and our health because it identifies problems that cause vehicle emissions to increase.

Frequently Asked Questions

What is OBD and how does it work?

OBD technology was developed in the 1980s by vehicle manufacturers to help technicians diagnose and service the computerized engine management systems of modern vehicles. A new generation of OBD (often referred to as OBD II) is present on 1996 and newer vehicles. All 1996 and newer vehicles now monitor the same components, use the same type of connector, use the same computer "language" and the same criteria for evaluating the powertrain systems and indicating problems to the driver and the repair technician.

OBD monitors all components that make up the engine management system. It can detect a malfunction or deterioration of these components usually well before the motorist becomes aware of any problem. When a problem that could cause a significant increase in emissions is detected, the OBD system turns on a dashboard warning light to alert the driver of the need to have the vehicle checked by a repair technician.

Which vehicles will be required to be checked?

1996 and newer vehicles having a gross vehicle weight rating of 8,500 pounds or less must have their OBD systems checked.

What equipment is needed to inspect OBD Systems?

A scan tool with generic OBD II capability is necessary to perform the required check. A scan tool is a very useful device which is commonly used to assist in the diagnosis and repair of a variety of vehicle problems. Many inspection stations already own scan tools which can also be used to perform the required OBD check, but those inspection stations which do not will need to have one in order to inspect 1996 and newer vehicles. At a minimum, scan tools must be capable of :

1. automatic initialization with any vehicle,
2. determining readiness status of OBD monitors,
3. determining malfunction indicator light status, and
4. retrieving diagnostic trouble codes.

Any scan tool which complies with Society of Automotive Engineers Recommended Practice J1978 is acceptable. Scan tools are available from a number of well known equipment manufacturers.

What is the cost of the equipment?

For those inspection stations which already have a scan tool with generic OBD II capability, no additional equipment will be needed. Inspection stations owning scan tools without generic OBD II capability can, in most cases, update their equipment to include OBD II capability for approximately $300 to $700, depending on the equipment manufacturer. Inspection stations with no scan tool can purchase generic OBD II-only scan tools starting at under $300, or full service scan tools with generic OBD II capability starting at under $1400. It may become necessary to upgrade scan tools that have generic OBD II capability in order to perform the required OBD check on newer and future model year vehicles.

What does the OBD check involve?

First, the vehicle is checked to see if the Malfunction Indicator Light (commonly called the "check engine" or "service engine soon" light) on the instrument panel illuminates when the ignition key is turned to the "on" position and then when the engine is running. Next, an electronic device known as a scan tool is connected to the vehicle, and used to communicate with the vehicle’s on board computer. The on board computer is checked to confirm that the vehicle is ready to be tested, to determine if the computer has attempted to turn on the Malfunction Indicator Light, and if applicable, to retrieve diagnostic trouble codes. The results are recorded, and the scan tool is disconnected from the vehicle. The entire OBD check typically takes less than 5 minutes.

Why is the OBD check needed?

Motor vehicles are the largest source of toxic and ozone-forming air pollutants in Vermont. While modern vehicles are getting much cleaner due to newer engine management technology and emission control components, emissions stay low only when all these systems are working properly. OBD technology helps to ensure that vehicles are operating as designed, and the OBD check ensures that the vehicle’s OBD system is doing its job.

What if my vehicle failed the OBD check?

If your vehicle failed, it must be repaired in order to receive a new inspection sticker. Your vehicle should be repaired by a qualified, trained automotive service technician equipped with the appropriate diagnostic and repair tools. Depending on your vehicle’s age and mileage, repairs may be covered by the vehicle manufacturer’s warranty. Refer to your vehicle owner’s manual for specific information on warranty coverage.

Following are possible reasons for failing the OBD check:

1. The vehicle’s OBD system connector has been removed or is otherwise not working properly. The OBD check cannot be completed if the connector is missing or is not working properly.
2. The Malfunction Indicator Light does not illuminate at all when the ignition key is turned to the "on" position. When the vehicle’s OBD system detects a problem it turns on the warning light to alert the driver to a problem. However, if the light can not illuminate because the bulb has burned out or is otherwise not working, the driver would not be alerted to the problem.
3. The Malfunction Indicator Light on the instrument panel is on (and/or commanded on by the vehicles’s on board computer) while the engine is running. This indicates that the OBD system has identified a problem which must be repaired. In this case, one or more diagnostic trouble codes will also be reported by the vehicle’s OBD system. These diagnostic trouble codes will help your technician diagnose and repair your vehicle.

What if my vehicle’s OBD system is "not ready"?

If your vehicle’s OBD system is not ready, the inspection of your vehicle’s OBD system cannot be completed. While this does not necessarily mean that your vehicle has a problem, it does indicate that your vehicle’s OBD system has not yet completed it’s tests, and problems may be present, but not yet identified. A recently disconnected or discharged (run down) battery, or recent servicing using a scan tool are the most likely reasons for a vehicle’s OBD system being "not ready." Note that there are a few vehicles which should not be rejected as "not ready". Ask your inspection station or the Department of Motor Vehicles for further information about these exceptions.

How do I get my vehicle’s OBD system "ready"?

The vehicle should be driven under a variety of normal operating conditions in order for the OBD system to become ready. These operating conditions include a mix of highway driving and stop and go, city type driving, and at least one overnight-off period. Your vehicle owner’s manual should provide more specific information on getting your vehicle’s OBD system ready.

Questions?

For more information about OBD contact the Department of Motor Vehicles at (802) 828-2067.

Additional Information From Vermont's Agency of Natural Resources

What does this have to do with vehicle air emissions?

Motor vehicles are the largest source of toxic and smog forming air pollutants in Vermont and North America. Modern vehicles are getting cleaner due to newer engine management technology and emission control components - but the emissions are only low when all these systems are in proper working order. When an engine is not running as efficiently as possible, performance is lost, fuel is wasted, and air emissions increase. OBD can detect problems that may not be noticeable upon visual inspection because many component failures can be electrical or even chemical in nature. By detecting component deterioration and/or failures, and alerting the driver to the need for potential repair, vehicles will be properly serviced before emissions become a problem, and before more serious and expensive problems develop.

Does OBD help consumers too?

OBD systems are designed to alert drivers when something in the engine management or emission control systems begins to deteriorate or fails. Early diagnosis followed by timely repair can often prevent more costly repairs to either electronic or mechanical powertrain components. For example, a poorly performing spark plug can cause the engine to misfire, a condition sometimes unnoticed by the driver. This engine misfire can, in turn, quickly degrade the performance of the catalytic converter. With OBD detection of the engine misfire, the driver would be faced with a relatively inexpensive spark plug repair. However, without OBD detection, the driver could be faced with an expensive catalytic converter repair in addition to the spark plug repair. In addition, manufacturers have increased incentive to build a higher quality vehicle with better performance, reduced emissions, and more efficient powertrains to prevent problems that can lead to OBD detection.

A vehicle identified by the OBD system as having a problem is running inefficiently - resulting in poor fuel economy and vehicle performance while shortening the life of the engine. OBD systems provide far more information than ever before to help auto technicians diagnose and properly repair vehicles during their first visit to the repair shop, saving time and money for consumers.

How does the driver know there is a problem?

When the OBD system determines that a problem exists, a corresponding “Diagnostic Trouble Code” is stored in the computer memory. The computer also illuminates a dashboard light indicating “Service Engine Soon” or “Check Engine” or displays an engine symbol. This light serves to inform the driver that a problem has been detected and vehicle service is needed. By law this dash-board light can only be used to indicate an actual problem. It cannot be used for example, as a reminder for regularly scheduled maintenance.

Then what?

When the car is delivered to the repair shop, a service technician can quickly retrieve the stored diagnostic trouble codes from the computer memory using a computer “Scan Tool.” By using this information, the technician can more quickly and accurately identify the problem and make the proper repair.

How can the dashboard light be turned off?

After fixing the problem, the service technician will turn off the dashboard light. There are also situations under which the vehicle’s OBD system can turn off the dashboard light automatically if the conditions that caused a problem are no longer present. If the OBD system evaluates a component or system three consecutive times and no longer detects the initial problem, the dashboard light will turn off automatically. As a result, drivers may see the dashboard light turn on and then turn off. For example, if the gas cap is not properly tightened after refueling, the OBD system can detect the vapor leak that exists from the cap not being completely tightened. If the gas cap is subsequently tightened, the dashboard light should be extinguished within a few days. This is not an indication of a faulty OBD system. In this example, the OBD system has properly diagnosed the problem and accordingly alerted the driver by illuminating the dash board light.

Can anyone service an OBD related problem?

Only qualified, trained technicians equipped with the appropriate diagnostic and repair equipment should conduct OBD related service. With the population of modern technology cars growing, all dealerships and independent repair shops should have qualified personnel for this service. Vehicle owners should ask at their service facility if the technicians have received proper training, and have access to the necessary equipment to properly service OBD equipped vehicles.

Will aftermarket parts work with OBD?

Most aftermarket parts should work with OBD systems. It is the responsibility of aftermarket parts manufacturers to ensure that their parts work properly with the vehicle for which they are designed. Aftermarket parts manufacturers who do a thorough job of replicating original equipment manufacture parts and those who carefully develop specialty parts will be able to produce parts that work with the OBD system.

Thank you for your cooperation and helping do your part to clean up the air.

Questions?

For more information about OBD or other Air Pollution issues, or to receive additional copies of this pamphlet, call the Air Pollution Control Division at (802) 241-3840

State of Vermont Agency of Natural Resources
Department of Environmental Conservation
Air Pollution Control Division
Mobile Sources Section
103 South Main Street
Waterbury, VT 05671-0402

Visit the Vermont Agency of Natural Resources - Air Pollution Control website at: http://www.anr.state.vt.us/air/