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On-Board Diagnostics Testing


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Check Engine Light Be as bright as this dashboard light!
Take your vehicle to a qualified OBD II repair shop when you see the Check Engine light.  A flashing light indicates a severe problem which could damage the catalytic converter.

Blue Dot  OBD II Early Detection System

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If your vehicle is a 1996 or newer model, it comes equipped with an On-Board Diagnostics System (OBD II). This system is designed to catch emissions problems before they become a major concern. This early detection system benefits you in two important ways:

  • It alerts you to a condition that can waste fuel, shorten engine life and result in potentially expensive repairs.
  • It lets you know your vehicle is contributing to unhealthful air by emitting pollutants in excess of federal standards.

Blue Dot  Emissions Tests with OBD II

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Your yearly smog check on 1996 and newer vehicles are now done through OBD II, rather than the traditional two-speed or "tail pipe"  test. OBD II is more accurate than the two-speed test and less costly than the dynamometer tests used in some other states. The test itself is also much faster. Stations can often complete an OBD II test in five minutes or less.

The emissions technician will scan your Vehicle Identification Number using a bar code reader. The technician will then plug a cable from the analyzer into your vehicle's OBD computer. There is no other connection or probe. Not only does this quickly indicate whether your vehicle passes, it also helps the technician pinpoint any malfunctions.

OBD II Cable
OBD II Test Screen

Nevada emissions inspections stations have been equipped with completely new analyzers which offer several new conveniences in addition to OBD II capabilities.  Simple screens walk the operator through the test. Software updates can be downloaded from the Internet.  Most important, OBD II tests are completed in less time than the tail pipe test.

OBD II is the lowest cost, most accurate inspection for new technology vehicles. Vehicles 1995 and earlier will continue to be tested under the two-speed method.


Blue Dot OBD Do's and Don'ts

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DO take your vehicle in for service right away if the “Check Engine” or “Service Engine Soon” light comes on and stays lit. This light should not be ignored. Even though the vehicle might seem to be running just fine, there is a problem evident which has potential to increase emission levels.

Sometimes when a Check Engine Light comes on the vehicle’s engine computer will go into a “back-up” or “limp-home” mode. This allows the vehicle to continue operating until repairs can be made. Back-up or limp-home modes are not the most emission or fuel efficient way for the vehicle to operate. The problem needs to be repaired.

DO check with your local dealer to find out if your vehicle is covered by warranty or recall if a problem occurs with your vehicle’s OBD-II system. Expensive emission components could be covered under warranty for up to 8 yrs or 80,000 miles, whichever occurs first.

DO get your annual emission test early. Remember, the test is valid for 90 days. If the emission test finds a problem with your vehicle, you will have some time to take care of the problem before your registration expires.

DON’T drive your vehicle if the “Check Engine” or “Service Engine Soon” light is flashing. A flashing light means that a problem exists that may cause damage to expensive emission control systems. So, get your vehicle to a repair facility immediately. A ruined catalytic converter can cost up to a couple thousand dollars to replace, depending on the vehicle.

DON’T take your vehicle in for an emission test right away if you just replaced a battery, or if the existing battery had gone dead, was disconnected or has been cranking slowly. If a battery drops below five volts the vehicle’s computer memory will be lost. Your vehicle will not pass the test and will be “Rejected”. The vehicle will need to be driven under varying conditions for up to one week in order for the OBD-2 system to run all of its on-board diagnostic tests.

If your license plates are expired, or will expire within the week, go to your nearest DMV office and request an operating permit. It is very rare to find a vehicle that will not be ready for emission testing after a week’s normal driving. In the event you have any questions, please contact the Department of Motor Vehicles Emission Control Lab in your area. In Las Vegas please call (702) 486-4981. In Reno please call (775) 684-3580.

DON’T clear any Data Trouble Codes using a scanner, hoping to pass the emission test in Nevada. If you erase the Data Trouble Codes and then take the vehicle in for emission testing right away, it will not emission test and will be “Rejected”. Clearing the Data Trouble Codes erases all of the OBD-2 systems memory settings and the vehicle will need to be driven normally for up to one week in order for the OBD-2 system to regain all memory and settings. Trying to pass an emission test by erasing Data Trouble Codes rarely achieves the desired results.


Blue Dot  On-Board Diagnostics FAQs

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What is OBD?
The On Board Diagnostics system is composed of a computer that monitors the emissions system and key engine components. It can usually detect a malfunction or deterioration in these components before the driver becomes aware of the problem. The U.S. EPA has required auto makers to install OBD systems on all cars and light-duty trucks made since 1996.

OBD systems are designed to alert the driver when a component in the engine management or emissions systems begins to deteriorate or malfunction. Early detection of minor problems, followed by timely repair, can often prevent more costly damage to components such as the catalytic converter.
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How does OBD work?
When the OBD computer detects a problem, it stores a Diagnostics Trouble Code and may illuminate the "Check Engine" or "Service Engine" light on the vehicle's dashboard. This light cannot be turned off until the necessary repairs are completed or the condition no longer exists.

When you take your car in for diagnosis or for an annual emissions inspection, the repair technician retrieves the trouble codes from the computer using a "Scan Tool."  By using this information, a properly trained repair technician can quickly and accurately fix any problem.

Under certain conditions, the dashboard light will blink or flash. This indicates a severe problem. The driver should reduce speed and seek service as soon as possible. Malfunctions which cause a flashing light can seriously damage emission control system components in a short period of time, especially the catalytic converter.
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What does OBD have to with do with air pollution?
Motor vehicles are the largest source of air pollutants in North America. Although modern vehicles are getting cleaner due to improved engines and emission controls, emissions are low only when everything is in proper working order. When an engine is not at maximum efficiency, performance is lost, fuel is wasted and air pollutant emissions increase. OBD can detect emission component problems before there is an obvious problem with the car or truck.
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How do I know there is a problem with my car or truck?
OBD systems are designed to alert drivers when something in the engine or emission control system begins to deteriorate or fail. When the OBD system determines that a problem exists a code is stored in the computer memory. The computer may illuminate a dashboard light indicating "Service Engine Soon" or "Check Engine."

This light informs the driver that there is an emission related engine problem. If the light is on, there is a real problem relating to emission control that needs to be fixed. If the light is flashing the driver needs to take the car to a repair technician as soon as possible.
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How do I turn the engine light off?
The repair technician will turn off the dashboard light after the necessary repairs have been made. There are also situations under which the vehicle’s OBD system can turn off the dashboard light automatically if the conditions that caused the problem are no longer present.
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Is OBD going to cost me more money?
No. It may actually save you money. OBD is designed to aid the driver as well as the environment by alerting the driver early to deterioration and failure of parts that affect engine function and/or pollutant emissions. Early detection of engine or emission system failures followed by a timely repair will prevent more costly repairs down the road. It can also help lower repair costs because the test is more specific and can help reduce troubleshooting time.
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What happens after an OBD test?
Vehicles that pass the OBD inspection will be able to proceed with vehicle registration. All emissions test results are transmitted electronically to the DMV. We encourage you to renew by Internet, at a kiosk or at emissions stations that offer this service. 

If a car or truck fails the OBD test, the owner will be provided with a test report that specifies the reason for failure. Vehicles that fail the OBD inspection test must be repaired in order to register the car or truck.
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Who can fix an OBD problem?
Only a qualified trained service technician equipped with the correct diagnostic and repair equipment can perform OBD related repairs. Vehicle owners should ask their vehicle repair facility if the technicians have received proper training and have access to the necessary equipment to properly service OBD equipped vehicles.
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Are OBD related repairs covered by my warranty?
Federal law requires that the emissions control systems on 1996 and newer vehicles be warranted for two years or 24,000 miles (which ever comes first). Many auto manufacturers provide extended coverage as well. Federal law also requires that the on-board computer and the catalytic converter on 1996 and newer vehicles be covered for 8 years or 80,000 miles. Consult your vehicle owners manual or warranty for coverage.
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