What is OBDII and how does it work? [Back to Top]
The first on-board diagnostic (OBD) systems were introduced in the early 1980's to lower vehicle emissions and help automotive repair technicians in the diagnostics and repair of computerized engine controls. As a results of improved technology, a new generation of OBD (OBDII) was developed for 1996 and newer vehicles. The new OBDII systems monitor the vehicle's electronic sensors and actuators while the vehicle is being driven to insure they are working "as designed" by the manufacturer. The on-board computer has the ability to identify a problem well before the driver is aware of any problems, such as lack of performance, high emissions, or poor fuel economy. Early detection helps avoid costly repairs and can improve the vehicle's emissions.
How is the driver notified? [Back to Top]
A light on the dash, called a Malfunction Indicator Lamp (MIL), will illuminate if an emissions related problem is detected. Below are some "MIL" examples since there is no standard MIL symbol being used by manufacturers.
Your vehicle's OBDII system will turn the MIL light "ON" when it finds a fault that may cause high engine or evaporative emissions. A flashing MIL, indicates a severe fault is occurring and that immediate service is needed to prevent expensive damage to the catalytic converter and ultimately resulting in higher emissions. (Check your owner's manual for detailed information.)
Do I have to go to the dealer to get my OBDII car fixed? [Back to Top]
No. Properly trained and equipped independent repair shops are capable of utilizing the diagnostic information from the OBDII system and can make repairs just like dealers. In fact, several of the provisions incorporated in the OBDII regulation are intended to make it easier for independent shops to diagnose and repair vehicles accurately and in a cost-effective manner. The Federal Clean Air Act requires that catalytic converters and Onboard Diagnostic devices on 1995 and newer vehicles be warranted for a minimum of 8 years or 80,000 miles.
What does a North Carolina emissions inspection consist of? [Back to Top]
A North Carolina emissions inspection consists of connecting a certified analyzer to the vehicle's OBDII system to verify that all vehicle emissions components/systems are working per the manufacturer specifications along with a visual safety/tamper inspection.
My Check Engine light is on, what does that mean? [Back to Top]
Most manufacturers advise having the vehicle serviced as soon as conveniently possible. Since there are many different problems that can cause the light to illuminate, it is hard to generalize how severe a problem may be. However, often the problem will have a noticeable effect on fuel economy, performance, or drivability of your vehicle, and extended driving without fixing the problem could possibly damage other components. Additionally, there are certain malfunctions that can cause the warning light to blink. This indicates that a malfunction is currently occurring which could be damaging your catalytic converter. Because replacement of the catalyst can be expensive, many manufacturers recommend having the vehicle serviced as soon as possible.
My MIL (check engine) light did not come on. What do I do now? [Back to Top]
The inspector mechanic is required to verify the MIL light bulb is working by turning on the key without starting the engine. A bulb not working as a result of being burned out bulb or due to a blown fuse will cause you to fail the emissions inspection.
My vehicle was rejected for being "Not Ready", what does that mean? [Back to Top]
On-Board Diagnostic II systems (OBDII) perform self-tests of their various emissions system components utilizing various monitors while the vehicle is driven. Therefore a vehicle that has received a North Carolina emissions inspection result of "not ready" due to recent maintenance or vehicle's battery replacement or disconnection must be driven to reset monitors to a ready status. These components are referred to as "readiness monitors" and identify whether the vehicle's computer has meet the vehicle manufacturer "enable criteria" conditions to run the required "diagnostic tests".
The following are suggestions that may help get your monitors to a "Ready" status:
My vehicle will not communicate, what does that mean? [Back to Top]
Communications between the certified emissions analyzer and your vehicle could not be established. Below are several suggestions that could be followed to ensure you receive a North Carolina emissions inspection:
What is a drive cycle? [Back to Top]
Vehicles equipped with an On-Board Diagnostic II (OBDII) perform self-test of their emission system utilizing various monitors while the vehicle is driven. These tests are referred to as "readiness monitors" and identify whether the vehicle's computer has meet the vehicle manufacturer "enable criteria" condition to run the required "diagnostic tests".
Your everyday driving patterns over a period of time should be sufficient to set all the monitors. If a North Carolina emissions inspection is required and your vehicle's battery is replaced or emission repairs were completed, the monitors will be set to "not ready" status. In this situation, your everyday driving pattern may not be sufficient to set required monitors in a short period of time. Therefore a manufacturer's "drive cycle" must be driven. This "drive cycle", which should not be performed by inexperience drivers, is designed to allow monitors to operate in a compressed time and distance drive pattern. The correct drive cycle for your vehicle can vary greatly depending on the vehicle model and are available from most auto manufacturers.
My check engine light is on and my annual emissions inspection is due. Should I get my vehicle repaired before bringing it in for an emissions inspection? [Back to Top]
If your emission inspection is due soon, have the vehicle inspected first. The vehicle will fail due to the MIL light being commanded on, but you will receive the Vehicle Inspection Receipt/Statement (VIRS), which will document the cause of the failure. You can then provide this information to your repair technician (repairs must be made within 60 days of the initial failure to receive a free re-inspection). If the vehicle then returns for re-inspection and fails a second time, you may be eligible for one-year waiver from DMV. See the question dealing with waivers qualifications below.
What does the gas cap have to do with emissions? [Back to Top]
If your gas cap is damaged or not tightened per manufacturer requirements, this will allow excess evaporative emissions to escape from the vehicle causing the evaporative monitor to set the MIL light. Corrective action would be to replace the gas cap if damaged, but most cases retightening will solve the problem.
How do I get a waiver? [Back to Top]
Waivers are available for vehicles unable to pass an emissions inspection test and are granted by authorized DMV personnel. A vehicle receiving a waiver is exempted from meeting the full requirements of the emissions test portion of the inspection for one year. For more information concerning waivers please contact your DMV License & Theft Bureau Office.
A parts waiver can be issued if an emission control devices has either been tampered or is inoperative and the part is no longer available.
A repair waiver can be issued when a vehicle cannot pass an emission inspection but the owner has made the attempt in correcting the emission failure. The following are the basic steps that need to be followed in order to be eligible for a repair waiver. The "OBDII Failure Brochure" which describes the repair waiver in more detail can be provided to you upon request from your inspection facility.
DMV personnel may issue three types of exemptions:
Contact your local DMV district office for more details (DMV License & Theft Bureau Office).
