What Is OBD



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What Is OBD?

What Is OBD?

OBD stands for On-Board Diagnostics a computer based system built into modern vehicles. OBD monitors the vehicle’s major components, including emission controls. The system provides drivers a warning of a failure of one of the monitored systems. The “Check Engine” or Malfunction Indicator Light (MIL) will illuminate in the event of a component or system failure. 

First a little history lesson is in order…….. 

            Beginning with the original Clean Air Act of 1963, the Federal Government passed legislation in an effort to improve air quality. The Clean Air Act Amendments of 1970 formed the Environmental Protection Agency (EPA) and gave the agency broad authority to regulate vehicle pollution. Specific responsibilities were set for government and private industry to reduce emissions. Since then the agency’s pollution and automotive emission standards have become increasingly more stringent.

            The EPA dictates the standards on what are acceptable limits for vehicle emissions. EPA guidelines state that all vehicles must reduce the emissions of certain pollutants and potentially harmful gases to acceptable levels.

            After Congress passed the Clean Air Act in 1970, the state of California created the California Air Resources Board (CARB). The role of CARB is to mandate stricter emission standards for vehicles sold in California. Several other states mostly in the Northeast have chosen to adopt CARB standards for vehicles sold in their states as well.

CARB began regulation of On Board Diagnostics for vehicles sold in California beginning in 1988. OBD 1, the first phase required monitoring of the fuel metering system and the Exhaust Gas Recirculation (EGR) system and additional emissions related electrical components. The MIL was required to alert the driver of a malfunction. 

In 1990 the Clean Air Act was amended. The Clean Air Act Amendments of 1990 added many new elements including: 

  • Stricter tailpipe emission standards for cars, trucks and buses
  • Stringent Inspection and Maintenance Programs in parts of the country where air quality is suffering 

With the passage of the Clean Air Act Amendments of 1990 CARB developed regulations for the second generation of On Board Diagnostics (OBDII). These amendments also prompted the EPA to develop somewhat different On Board Diagnostic requirements. 

So what does all this mean? 

Most 1988 and newer vehicles will have a Malfunction Indicator Light (MIL). This light if illuminated, means there is a malfunction of the emissions control system. Unfortunately, there could be hundred or more possible malfunctions. Thorough testing needs to be done to identify the cause.

            Most manufacturers will print in the owners’ manual of the vehicle that the car can still be driven but should get service as soon as possible to identify the cause. Most 1996 vehicles will flash the MIL in the event of a catalyst-damaging misfire. This is important to know because this indicates the engine is misfiring so bad that it can harm the vehicles catalytic converter, which could lead to further costs to repair. Very prompt attention to a flashing MIL is essential.


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