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Onboard Diagnostics

Onboard Diagnostics (OBD II) is a computer-based system that monitors the performance of a vehicle's powertrain (engine, transmission) and emission control systems. The federal 1990 Clean Air Act Amendments required vehicle manufacturers to install OBD II in light duty cars and trucks starting with model year 1996. NYS requires annual OBD II emissions inspections for applicable non-diesel and non-electric vehicles under the New York Vehicle Inspection Program (NYVIP). Model year 1997 and newer light-duty diesel vehicles are subject to NYVIP OBD II. The NYVIP OBD II inspection requires connecting approved inspection equipment to the vehicle's OBD connector to download emissions system information.

OBD II offers several advantages over traditional tailpipe-based emissions inspections. OBD II alerts the driver, by illuminating the MIL, of an engine management or emissions control issue once it's been encountered. There are circumstances where the OBD II system may detect a problem before the driver notices an operational issue. Early diagnosis and timely repairs can prevent additional and even more expensive repairs.

OBD II also provides the repair technician with information (diagnostic fault codes, freeze frame information) specific to the emissions fault condition that led to MIL illumination. This information allows for a more focused and potentially faster repair.

When an engine is not running as efficiently as possible, performance can be lost, fuel can be wasted, and air emissions are likely to increase. OBD II repairs can result in substantial fuel savings.

OBD II inspections take less time to complete than traditional tailpipe based inspections, and are capable of evaluating evaporative emissions problems (i.e., leaks from hoses) that are not possible for older, pre-OBD II vehicles.

Important OBD II Facts

  • If your car or truck was manufactured in 1996 or later, it has a built-in OBD II computer system that monitors the engine and emissions control system.
  • If the OBD II system detects a problem that could cause elevated emissions, it alerts the driver by illuminating the malfunction indicator lamp (MIL) or "Check Engine" light.
  • If the "Check Engine" light comes on, you should have your car serviced by a professional technician as soon as possible. OBD II can assist technicians identify and repair problems by storing a "trouble code" and "freeze frame" data for the malfunction.
  • OBD II technology can prevent costly repairs by flagging problems before they become major. Responding to the "Check Engine" light in a timely fashion can improve fuel efficiency, enhance your vehicle's performance, and protect the environment by reducing vehicle emissions. While newer OBD II vehicles are designed and manufactured to meet cleaner emissions standards, their emissions will only remain low if these vehicles are properly maintained.

Malfunction Indicator Lights (MIL)

The MIL is located on the vehicle's dashboard. When lit, it can be red, amber, or yellow and can read "Check Engine," "Service Engine Soon," or simply be an image of an engine.

Sample of a check engine light - the shape of an engineAnother sample of a check engine light.Sample of a service engine soon light

Certain severe engine malfunctions may cause the MIL to blink or flash on and off. These conditions require a reduction in speed and immediate service. Consult your owner's manual for further guidance.

If the MIL remains lit while the engine is running, the vehicle's OBD II has detected a potential emissions related fault that needs to be evaluated. The problem may increase air pollution, reduce fuel efficiency, or even harm the engine. You should take the vehicle to a qualified automotive repair technician to determine the severity of the problem as soon as a possible.

A loose gas cap may cause the MIL to turn on. Most OBD II vehicles complete a series of manufacturer-defined diagnostic checks for evaporative gas leaks. A broken gas cap, or a gas cap not completely tightened, can cause the MIL to light. If you believe the gas cap was not completely fastened, simply re-tighten the cap.

There may be cases where the MIL goes out before any repairs are made. If the condition that initially caused the MIL to light has been addressed (for instance, a loose gas cap was tightened), the OBD II system is capable of turning the MIL off. This sequence of MIL on/MIL off does not indicate a defective OBD II system. Your vehicle needs no special attention unless the MIL comes on again.

Do not disconnect the battery in an attempt to bypass the OBD II. This will lead to an inspection failure.

A vehicle presented for an official NYVIP OBD II inspection with an illuminated MIL will fail the emissions inspection. Do not wait until the end of your current inspection sticker to have your vehicle inspected. Your repair technician needs adequate time to diagnose and repair the vehicle.

What to expect during your NYVIP OBD II Inspection

The complete NYVIP OBD II inspection includes three components:

  • Safety inspection;
  • Visual inspection of the emission control devices (including the gas cap); and
  • OBD II inspection.

The NYVIP inspection involves two visual inspections followed by retrieving the electronic data from the vehicle's on-board computer. The visual inspections include safety components, and emission control devices such as the gas cap and MIL. Electronic OBD II data is retrieved by attaching the inspection equipment to a connector inside the vehicle. The OBD II pass/fail determination is based on the visual inspections and the data retrieved The inspection equipment will print a Vehicle Inspection Receipt that details the results of the inspection. You can request this document from the inspector.

If your vehicle passes the inspection, you will receive an inspection sticker that is affixed to the vehicle's windshield.

If your vehicle fails the inspection, the print out will list the reason(s) for the failure. The report can also provide useful information to a qualified automotive repair technician should your vehicle require repair.

What to do if your vehicle fails its inspection

Your vehicle must pass a re-inspection or receive an emissions-related waiver (see below) in order to receive a valid inspection certificate (sticker). In most cases, the vehicle will need to be repaired. Failure to pass the inspection by the expiration of the current inspection sticker will leave the motorist subject to fines and possibly registration denial.

If your vehicle failed for the readiness evaluation, it means that the inspection equipment communicated with the vehicle and the vehicle reported that it had not completed a sufficient number of on-board diagnostics. The vehicle will need to be driven until a sufficient number of diagnostics are run to completion. Motorists receiving a 10-day extension should be cautioned that this extension is for one time only. The vehicle should be driven for several days to set monitors and then be re-inspected.

NYVIP2 (leaves DEC) has additional information on readiness failures.

NYVIP OBD II Inspection Emissions Waivers

Vehicles subject to the NYVIP OBD II inspection may qualify for a waiver if all of the following conditions are met:

  • the vehicle fails only the OBD II emissions test portion of the inspection (i.e., the vehicle must pass the safety, gas cap check, and emission control device visual checks);
  • the vehicle receives repairs related to the reason(s) for the OBD II emissions failure;
  • the vehicle fails the OBD II inspection at least twice during its current inspection cycle (i.e., an initial inspection and at least 1 re-inspection); and
  • any qualifying repairs must be documented and must total at least $450.

Emissions-related repair costs may be covered under the vehicle manufacturer's warranty. Warranty coverage varies depending on what components require repair, vehicle age, mileage, and the individual vehicle manufacturer's warranty provisions.

The federal Clean Air Act requires an 8-year or 80,000 mile warranty on the major emissions control components, such as the catalytic converter, and a 2-year or 24,000 mile warranty on other emissions control components. Owners are advised to read the warranty provisions within their owner's manual or warranty booklet.